Dom and Mel face one of their toughest challenges yet: dealing with a builder who may well offer the worst value for money in Britain. The problem is, no one knows where he is...

Christophe and Debra Montoya-Timperley have lived in their three-bedroom semi for ten years. But as their sons, Joshua and Max became older, the family had outgrown the house. So in 2008, they embarked on what they hoped would be a life-changing building project. The couple agreed to the builder's quote of £69,000. But after they had handed over £26,300 of their hard-earned cash, twelve weeks into the job the build came to standstill and the builder vanished without a trace – before he had even dug the foundations! The Montoya-Timperleys won a County Court settlement of £32,000, but they have never been able to track down the builder to get their money back.

So Dom has a particularly tricky manhunt on his hands.He has to use all his cunning to find the builder and lure him into a carefully laid trap.

Meanwhile, Melinda and her team face a huge challenge. Normally she is tasked with rectifying the mess a builder has left behind, but building an extension from the ground up is a first.

When Karen and Tristan Crook got married in 2011, they did not have to look far to find their first marital home. Karen's grandmother had recently passed away, leaving behind her 1920s semi. The couple decided to buy out her parents and other relatives and become the new owners of the family home.

The house needed modernisation so they planned to update the rooms, convert the loft and build a rear extension. They were sure they had found a builder they could trust, as he was an ex-boyfriend from Karen's teenage years. The builder assured them he could do the whole job for £68,000, and quickly got on with ripping everything out. Only trouble is, he did not do much putting back! Four months on, the builder had walked off site with £41,000 of their money, without having started the loft conversion or the extension and leaving their treasured family home gutted.

Melinda has a mountain to climb if she is going to get Karen and Tristan into their home – she even resorts to sending out her builder John in search of free materials. Meanwhile, Dom finds out that Karen's ex-boyfriend is a cowboy who is a master of excuses...

Dom and Mel are in Cramlington, just a few miles north of Newcastle, where they face a 'Cowboy Builders' record: a house with more problems than they have ever encountered. In 2010, Michelle and Dominic Cairns planned to start a family and an unforeseen inheritance gave them the chance to transform their home. The couple chose a builder and a few months into the job they discovered they were expecting their first baby. But the builder then walked off the site, leaving them with a list from the local council's building control department that contained 103 defects and recommendations. Mel has her work cut out tackling the problems and soon discovers another spanner in theworks. It transpires that the builder didn't block off the rainwater drain before pouring in the foundations, so the drains are now blocked with concrete. With all of her efforts diverted to sorting out this unexpected problem, Melinda has a fight on her hands if she is going to deliver the nursery, which would mean so much to the Cairns. Meanwhile, Dom is hot on the heels of the builder. He discovers that not only is he a fan of the show, but he has made some classic cowboy errors. When Dom find that he is in the process of starting up a new company, he knows that it is definitely time to act...

Dom and Melinda are in Milton Keynes, helping out a family who were left with nowhere to wash themselves but the kitchen sink. In 2011, Kate Snow, husband Mike and their two sons Henry, 20, and Richard, 17, wanted to adapt their three-bedroom home. Kate suffers from chronic degenerative spinal arthritis, and a ground-floor office for their home business and a disabled access wetroom were vital. They pulled together their life savings and paid a local building company £34,000 to convert their garage, existing bathroom and downstairs toilet, with some additional work to the driveway and garden. It should have been a simple six-week job... Six months later, the builder walked off with their money, leaving the family with an unfinished, uninsulated, unsafe mess. It looks like a straightforward job for Melinda and her team, until they discover that nothing is as simple as it seems. Meanwhile, Dom uncovers a trail of debts and broken promises left by the builder, stretching across the Midlands and beyond. For once it looks like the cowboy is one step ahead, as he tries to pay off his victims to stop them talking...

Single mum Rosanne lives in Bath with her son. Rosanne wanted to extend her cottage, but after paying all of the money to the builder, Rosanne was left with an unfinished shell.

Dom and Melinda head back to Harrow to visit a family they helped back in 2010 and find out whether the cowboy responsible has received his just deserts. College lecturer Rae Green had decided to extend his three-bedroom terraced house in Harrow when his elderly father Tony, a Parkinson’s sufferer, moved in. With wife Jenny and children Shamarr, Achish and Janai also in the house, the family desperately needed a loft conversion and a kitchen extension to give them the space they desired. A recommended builder quoted £34,400 for the work, so they took the plunge and remortgaged their house in order to fund the project. After two troubled months, the builder did a runner with £28,000 of the Greens' money, claiming that the taxman was shutting him down. The Greens were left in the chaos that their cowboy builder had left behind. For 84-year-old Tony, this meant sharing a cramped bunk bed with his teenage grandson. While Mel fought tooth and nail to give the family a comfortable home, Dom discovered that the builder was one of the most prolific cowboys he had ever encountered. He uncovered a string of other families who had lost their money and had heard the same excuses – but all at different times, proving that the builder's sob-story was a pack of lies. Two years on, Melinda is back to see how life has been for the Green family. Meanwhile, Dom finds out that the cowboy has been up to his old tricks. Will he get the justice he so richly deserves?