Ju-Ju, a unisex fashion store run by fortysomethings Soly and Tim, have been fronting their distinctively-designed business in Brighton’s famous Laines area for more than a decade, and it’s started to show. They’re surrounded by potential customers, ‘fashion rebels’ - distinctive dressers with money to burn - but instead only offer cheap student garb to a dwindling clientele.

Diane Lazzaris runs One One Seven, a Surrey boutique which recently made an annual loss of 100,000 pounds. Concerned that the shop appears to lack passion and flair, Mary takes Diane to a Chelsea boutique for some presentation inspiration before testing her styling skills during a magazine photoshoot. Can One One Seven be saved, or is its number truly up?

Mary is in Doncaster to help turn around Homeboy, a boutique trying to sell menswear and womenswear to the party crowd. Owner Cath Taylor blames the arrival of a new shopping centre for the downturn in her fortunes. But with celebrity collections in large fashion retailers, Mary has got to give Homeboy an entirely new image if it's going to compete.

Mary is in Islington, North London at Comfort and Joy, which is run by divorcees Ruth Llewellyn and Anthony Wilson. It's too late to save their marriage, but Mary thinks she can help rescue their shop and make it a beacon of fashion on the high street.

To start the series, Mary visits the wealthy town of Ascot. Its High Street is home to Blinkz, a shop that caters for the fuller-figured woman, owned by size 10 gym fanatic Amanda Collins. Mary is shocked to discover that Amanda's attitude to her plus-size customers leaves a lot to be desired. Blinkz is full of dowdy, baggy, unflattering clothes that most people, whatever their size, wouldn't be seen dead in. As a result nothing is selling and the business is in crisis.

Cardiff presents Mary with her most difficult challenge to date. Kelvin Evans, owner of a boutique and bar called Floyds, has very firm ideas about the retail business. Run by his partner Sharon Hunt, Floyds sells cheap end-of-line clothes and tacky accessories. The women of Cardiff are giving Floyds a wide berth, but Kelvin cannot understand why. Not one to mince her words, Mary lays it on the line and tempers flare.

Burt's Men's Store in Chorlton has been in Adrian Burt's family for 112 years but under his leadership the store's takings are worse than they've ever been. Mary Portas is determined that this store deserves a place on our high street but it's going to be a massive upheaval for the staff - one of whom has been working there for 33 years. She's got to bring the outdated Burt's team up to speed on 20 years of men's fashion.

Three years ago professional stylist Becky Eleazu realised her dream and opened Rumplestiltskin, a hip fashion boutique in an up and coming part of South London but when her boutique failed to attract the stylish locals she asked her partner Max, a personal trainer with no fashion experience, for help. Max has the gift of the gab but when it comes to fashion he's way out of his depth. The shop looks like a youth club and the clothes are way to "street" for the young professionals Becky wants to attract. Right now those shoppers are getting their fashion fix in London's West End and to get them to shop local is going to take a miracle - or some magic - from Mary.

Lucy Weller, a former theatre set designer, owns and runs Selkie, a ladies' fashion boutique in the centre of York. A fabulous building and a wonderful location haven't been enough to attract York's sophisticated forty-somethings over the threshold.

This week Mary visits two shops she helped put on the right track in the last series. Ju-Ju, a Brighton based fashion boutique, owned by Tim Price and Soly Daneshmand, had completely lost its way and was haemorrhaging money. and Doncaster-based shop Homeboy, which she'd renamed Seen as part of her strategy when she first visited last year. The shop had been struggling in the face of stiff competition from a new shopping centre that had opened in the town. But owner Cath Taylor had also lost sight of her customer and was not offering what the 'disciples of Beckham' tribe were after.

Mary takes on a struggling London bakery in a battle that ends in tears when she encounters one of the feistiest shopkeepers yet. Maher and Sons has been in business for 36 years but profits have halved in the previous five.

Mary tackles Chris and Juliet, a London couple who are running a beautiful Dorset village shop into the ground. The couple bought Clealls of Corfe Castle a year ago, but are haemorrhaging almost 6,000 pounds a month and now stand to lose their savings, their pension and their home. The shop is more mini-mart than country store, and the locals and tourists are heading for the hills.

Mary focuses upon the most endangered sector of all - greengrocers. She finds a store in Merseyside on its knees, and takes on three fiery sisters that are running it into the ground. Fosters has been open 115 years, but the sisters who recently bought it are clueless, prickly and think they know best.

Mary battles to save a Kingston homeware shop living on borrowed time. Their 1970s stock is shockingly bad, the hippy owners are from another planet, and it may be almost impossible to bring them back down to earth.

Mary takes on an 80s hairdressing legend whose business is facing the chop. She is in Rochdale, one of the cities worst hit during the recession, and on the edge of town is the once-great John Peers hair salon, now teetering on the edge of oblivion.

Mary tries to fix a broken down Surrey DIY store - but the owner seems to have a screw loose! He's seems to have forgotten the nuts and bolts of his business, and it's up to Mary to hammer home some sense.