During the final push of the Dominion War, Captain Ian Quincy Knapp, commanding the USS Devonshire, encounters an unknown, powerful, and malevolent new force in the McAllister Nebula.

The mysteries of the Briar Patch beckon to the crew of the USS Excelsior, under the command of Captain Ian Quincy Knapp and his new senior staff. Their first mission has them looking for an foe that Knapp already has some knowledge of, but what they will discover will shock them all.

The Excelsior leads a task force after the Grey, but her crew quickly realizes they got more than what they bargained for!

The Independence is caught in 29th century intrigue when the crew discovers a legendary event in the past may have occurred due to tampering with the timeline.

Captain Knapp briefly clashes with new XO Elizabeth Shelby's attitude, before the Excelsior heads off to investigate the disappearance of the Nova-class USS Perihelion. Arriving at the ship's last known coordinates, they discover the ship in an impossibly close orbit of a quantum singularity, alongside an unknown vessel that dwarfs the Excelsior. But when an investigation reveals the strange, deleterious effects that the singularity had on the Perihelion crew and now the Excelsior crew as well, they realize what the ramifications could be for the entire galaxy.

The Grey are back, but the only one who can stop them may not be willing to help.

Captain Knapp welcomes two representative of the planet Tren'La, who have had centuries of experiences with the Grey, Princess Illiana and her son, Aris. Fleeing a Grey attack, they appeal to the Federation for help, although Admiral Nechayev must turn down their request, despite the advantages their spatial fold drive may bring. But when Aris and recent Academy graduate Artim Ibanya discover Grey troops on Ba'ku, Knapp must take command of the fleet to fight off a Grey attack against Deep Space 12.

A glimpse at what could have happened if the original Excelsior, under Captain Hikaru Sulu, had found itself falling through a temporal anomaly on its way to assist Captain Kirk at Camp Khitomer. The Federation has fallen to the Borg, having been punished by the Q Continuum for their massive retaliatory strike against the weakened Klingon Empire after the assassination of the Federation President. What remains is being lead by the Battlestar-class USS Excelsior, as they search for a safe haven, but the arrival of the original Excelsior may provide a way to do more then simply survive.

Relationships with the Dominion come under threat when Captain Knapp is accused of killing a Founder serving as an ambassador to the Federation, while on a mission to help learn more about the Grey. Commander Shelby is put in the uncomfortable position of acting as the prosecutor in the informal investigative hearing held aboard Deep Space 12.

While transporting the Excelsior's new Security Chief, Lieutenant Luko, back to Deep Space 12, Lefler and her team are abducted by Orion Syndicate pirates who want her help in siphoning off a dangerous explosive byproduct of warp engines from a derelict Starfleet vessel.

Investigating the destruction of the terraforming vessel Encke in orbit of Osiris III, the Excelsior takes aboard Mission Specialist Corey Aster, an old Academy classmate of Ro and Rawlins. Ro is made uncomfortable when he realizes Aster still has feelings for him that he demonstrated while at the Academy, but the two are soon working together to identify what really happened to the Encke.

With the science mission on Ba'ku now under the control of Starfleet Medical, Ensign Artim Ibanya spends some time on Excelsior as he considers whenever to take a position on a science facility on Danula II. He tells Counselor Elbrey a tale of his life just before he went off to join the Academy, of how he became interested in Starfleet, met a young Lieutenant Jason Munoz, and foiled a plot of the Breen.

Luko rescues Traya, a young girl who happens to be Captain Knapp's daughter, from an Orion Syndicate slave planet, but come under attack from a squadron of Grey attack fighters. Excelsior manages to fend of an attack, but suffers damage that makes them unable to jump to warp. Soon, they are easy pickings for another Grey attack, which leaves the ship disabled and the crew, scattered throughout, attempting to avert a series of calamities long enough to restore power before a Grey battleship can move in for the kill.

An Andorian crew member is the only casualty when a conduit accidentally ruptures on the Excelsior. Radiation causes brain damage that results in a permanent case of clinical depression. While Henglaar looks into medical avenues to help the crewman and Counselor Elbrey does her best to keep him motivated, Captain Knapp also gets involved, lest the depression become too much and he becomes a danger to himself, and others around him.

Aris and Illiana are stunned when Kaz, Illiana's husband, arrives at the station, but he brings news of a massing Grey armada. As Starfleet prepares to intercept the threat, Captain Knapp is relieved of command of the Excelsior, while a Board of Inquiry prepares to judge his conduct regarding the damage Excelsior took while rescuing Traya during the events of HF 2.07 - "Fire In The Heart".

With DS12 surrounded by three Grey battleships, Admiral Nechayev orders the shields fortified. She notes that they are not without resources, but Commander Darwin suggests that with the fleet away, they don't stand a chance. Knapp then reminds them that not all the ships are gone. Nechayev asks him if he has a plan - Knapp says he'd better by the time he gets to the docking ring.

The Grey battleships and Captain Knapp are trapped in fold space and the fleet has returned to Deep Space 12. While a debate erupts about whether they should attempt to recover the Captain without releasing the Grey, Commander Shelby and Aris mount a risky rescue operation that has long-term consequences.

The Independence becomes entangled in a cat-and-mouse game that leads them to ancient archaeological artifacts indigenous to the Briar Patch. Meanwhile, Commodore Knapp and Traya spend some quality time together on a shuttlecraft. Back on Deep Space 12, meanwhile, Lieutenant Commander Lefler is haunted by her capture by Sha'kev the previous year - the nightmare worsens when Sha'kev sends her a cryptic message of his imminent return.

After having a vision of a Borg attack, Corey Aster tells Counselor Elbrey of a mission he was on, while aboard the Olympus, when they encountered the Collective.

Son'a Ambassador O'Faur comes to DS12, engaging in an abrupt meeting with Commodore Knapp and Admiral Nechayev. She shows them an image of a Cardassian shipyard constructed within Son’a territory at the edge of the Briar Patch. When Knapp asks whether the Ambassador has lodged a complaint the Cardassian government, she notes that the territory is in dispute from before the Dominion War. She then threatens that if the Federation does not intervene, they cannot be held responsible for the consequences.

As Ian Knapp, Myra Elbrey and Traya Knapp are preparing to celebrate the Earth tradition of Christmas, a surprise visitor arrives on the station. Someone is keeping an eye on the Briar Patch and is not saying why.

The Excelsior is called in to mediate a dispute between two sets of colonists after the death of one of the Federation colonists in an accident. A fundemental cultural difference threatens everything they have built. Meanwhile Ro Nevin is struggling with the concept of a relationship with Corey Aster.

Encountering a Ferengi trader, Shelby authorizes Luko and Lefler to obtain an old Starfleet ship. Returning the ship to DS12, Lefler assembles a team to return the old ship to active status and are granted permission to take the ship out for a cruise. But things never work out simply when they receive a distress call, and find themselves the only available help for an endangered science vessel.

"Captain's Log, Supplemental: We're en route to the Grey Research Facility after receiving an urgent distress call. All attempts at long-range communication have failed."

"Captain's Log, Supplemental: We're en route to the Grey Research Facility after receiving an urgent distress call. All attempts at long-range communication have failed."

While enroute to diplomatic negotiations on DS9, Admiral Nechayev and her away team of Excelsior personnel are kidnapped by pirates commanded by rogue Starfleet officer, onboard a stolen Federation starship. Meanwhile, Captain Shelby takes the Excelsior to assist the Cardassians in identifying where the pirates work from, as tensions with the Son'a increase.

"Captain's Log, Stardate 57324.6: With the Yridian drug runners in custody, we've tracked their last visit to the Federation colony on Bovina VIII. It appears the Yridians weren't just smugglers, but users of the Orion's cargo."

Lieutenant Corey Aster and Ensign Andrew Barrett are temporarily reassigned to the USS Aldrin on a routine terraforming mission on the edges of the Briar Patch. But when they discover a mass grave of hundreds of Bajoran refugees, they must look for answers when the Cardassians are implicated in their deaths. Aster grows close to one of the Cardassian scientists, and comes into conflict with Ro Nevin, especially since his grandfather was one of the victims of the massacre.

The Federation discovers suspicious fleet movements by the Tholians and believe it is a precursor to launching an attack to steal the Cardassian Tetrahedron. Attempting to warn the Cardassians and make preparations to join forces to stop it falls on deaf ears. The Federation decides to lay in wait outside of Cardassian space for the attack they are certain is coming.

The Independence prepares to become the first starship to enter and explore the subspace currents that allow warp travel in the Briar Patch. Officers from the Excelsior investigating strange readings on Ba'ku run into an old enemy. Dr. Henglaar faces some personal demons when his ex-fiancée, Independence Chief Engineer Sou, arrives on board with her husband, CMO Qu'Qul. But when Qu'Qul realizes his wife still has feelings for the Tellarite doctor, he challenges Henglaar to a Klingon ritual for Sou’s affection.

With Princess Illiana on board, the Independence begins its mission into the currents, but soon encounter Grey forces as they abduct citizens of an inhabited planet within the Briar Patch. Examining an abductee, Cole and her crew find evidence that suggests that the Grey have been a threat to the Federation for longer than previously realized. The Excelsior gives chase to a Breen vessel they believe may be carrying the fugitive Vorina. Henglaar and Qu'Qul prepare for their holodeck showdown, despite Sou’s objections.

While exploring the currents in the Briar Patch, the Excelsior crew realize the Tholians have a greater presence in the patch than previously thought. An ambush on a planet surface leaves Barrett racked with guilt and it's up to his friends and colleagues to rally round him. Meanwhile, a diplomatic conference with the Tholian Ambassador raises more questons than answers.

The Federation considers using Centris III as a listening post. The planet is believed to be uninhabited and offers a perfect chance for some well-deserved shore leave. "The Camping Trip Mission" begins and Barrett, Ro and Aster get more than they bargained for. The camping trip becomes a life and death battle for one of the team.

While the Excelsior attempts to lend assistance to a longtime member of the Federation, Security Chief Matt McCabe finds develops suspicions that do not endear him to the world’s rulers. He grows close to a local security officer while they investigate the supposed terrorist activities that the planet is suffering from. Soon, they stumble onto something far more dangerous.

Captain Shelby experiences a personal loss, while the rest of Excelsior’s crew uncovers some of the secrets of the Grey. Naros history with Tren'La make working with Princess Illiana difficult, as they discover more clues that link the Grey with the tetrahedrons.

Knapp and Naros lead the Antietam on a surveillance mission that gets out of control, while Zen and Aster's relationship is threatened by someone from the Trill's past.

The Tholians finally make their move, and the galaxy will never be the same. Commodore Knapp deals with a rebellious daughter.

Myra Elbrey hesitantly welcomes a former student of hers to Excelsior, when Milo Surgant arrives to act as a translator for the Horta exogeologist Lt. Pergium arrives to make some headway on the studies of the Ba’ku tetrahedron. But as the mission preparations begin, she realises that her old fears of him abusing his Betazoid talents may still hold true. When she is telepathically attacked in an act of revenge, Henglaar finally begins to understand the depth of his feelings for her.

Learn what life is like aboard Deep Space 12, as Excelsior's crew copes with the stress of battle ever looming on the horizon. This episode is primarily focused on character interaction; however, it can be said to contain three separate "threads" running in parallel.

The Tholians make their move: Siroc tests a new weapon against Starfleet, while the largest meeting of Alpha Quadrant powers since the Dominion War is not going so well. They know they need to band together against the Tholians but the Federation is keeping secrets from its allies. The illegally joined Trill, Zen, has difficulty with his symbiont while the first-ever portrayed Tellarite Captain faces down the Tholians' deadly weapon.

To better understand the tetrahedrons operation, an interrogation of the Orion Syndicate pirate Mason is conducted. When he reveals the location of another tetrahedron key, a mission is set up to retrieve it, with his help. But one of the officers will not return, and the others will be left reeling at the loss of one of their own. Shelby encounters a few ghosts of her own, when assigned to assist a Romulan fleet make the necessary adjustments to traverse the Patch, and runs into her former lover, Captain Mackenzie Calhoun.

In preparation for the major attack the Alliance is about to undertake, Knapp promotes Naros to the command of the USS Helena, while taking command of the fleet itself from Excelsior. Realising Siroc may try anything to get to the Grey Dyson Sphere, Naros realises not is he a target, but so are Elbrey and Artim, while Shelby works on making sure her senior staff deal with the raw emotion of the loss of one of their own. Meanwhile, Siroc sets his own plan in motion to disrupt the incoming attack forces.

The battle has been lost, and now the crew of the USS Excelsior struggles for their lives. With the battle plan shattered, and the enemy manuvering to annihilate them, no one is safe from the clutches of Siroc and the Tholian Assembly.

The Allied fleet makes further preparations to counter Siroc's next move, whatever it may be. But with the Grey continuing to be a no-show in the struggle for the tetrahedrons and Dyson Sphere, the fate of Admiral Knapp's daughter hanging in the balance, and Barrett's friends still struggling with his MIA status, things are beginning to rush headlong into a breakdown.

Tetrahedron research is continuing, but without vital assistance from people in Dao's past, gathering key information about locating and protecting the other Tetrahedrons has stalled out. Dao volunteers to return home and obtain further assistance from his former colleagues; but this mission may very well cost him his life, and the life of his host.

When sudden and brutal attacks by the Tholians and Breen begin to target both Starfleet and civilian craft alike, Captain Shelby must begin to battle for the hearts and minds of the Federation's closest allies. Meanwhile, Admiral Cole is confronted with overwhelming odds and an increasingly restless civilian crew in a desperate battle to survive.

Captain Shelby's leadership of the Allied forces is questioned, and Shelby is ordered to rest. Corey and Nevin consider an affair. Admiral Knapp, Pelas, and Lieutenant McFarland continue the search for Traya with no luck. S'Tal and Lieutenant McCabe miss Andrew. Captain Naros and Jorian Zen continue the search for Tesla Mor.

Old enemies, old friends, and old ideas are shaken up as Siroc's plans shift ever closer to their devestating conclusion; things are collapsing right under the feet of the Allies as he draws nearer to his victory. Meanwhile, Shelby has to face up to the toughest challenge of her career with less help than she's ever had, Dao must face his past if he has any hope of going into the future, and the prisoners must make their stand if they hope to survive the seemingly mindless brutality of Siroc and his henchmen.

Shelby's recovered the hearts and minds of Starfleet's allies against Siroc and the Tholians - but it may be too late. With the return of an old friend and the loss of new ones under tragic circumstances, Excelsior is in a desperate race to get back to her home station, as the entire patch has suddenly gone deathly silent. If things weren't bad enough, it has come down to the wire for Naros' race to beat Siroc to the Dyson Sphere and stop him from carrying out his mission. With Ro's capture, Siroc's entire checklist for his final plan is complete, and using the stolen memories from Counselor Elbrey, all that's left is getting there first.

The stunning conclusion to the Star Trek: Hidden Frontier series. The Station is under siege by the Grey once more, as the crew of the USS Helena struggle to catch Siroc before he arrives at the Dyson Sphere. While the battle rages outside, Shelby and Lefler are leading a skeleton crew of 93 in a desperate ploy to restore the USS Excelsior and rejoin the fight to protect the station's civilians. With time completely gone, all hope lies in Admiral Knapp, Martinez, Jorian (Zen) Dao, Corey Aster and Jenna McFarland being able to figure out how to use the Hybrid ship; but things are far more different - and deadly - than they seem. With Ro as their captive and unwilling source of the technical data needed, Siroc and Betras arrive on the Dyson Sphere, and Siroc will stop at nothing to get to the secrets of the Dyson Sphere. Tolian Naros, along with Faisal, Henglaar, Elbrey, and others also arrive to try to rescue Ro Nevin and stop Siroc from bringing on the potential destruction of the universe.