Dom and Melinda are in Balham to help a pair of newlyweds who had plans to extend their ground floor flat. Following the death of her mother, Sarah and her partner Stuart decided to use the inheritance money to extend their home in south London. They paid their builders £85,000 of a £95,000 contract, but were left with an unfinished shell and severe structural problems. Due to shoddy building work, the entire three-storey block of flats in which the couple live is in danger of collapse.

The state of the building is so bad that before Dom and Melinda are even allowed access to the building, a structural engineer insists that emergency props are installed to safely support the walls.

Melinda and her team plan to fix the botched work and complete the extension. However, these efforts are thwarted at every turn, as at each stage of the repairs yet more problems are uncovered. Will the team be able to overcome these obstacles to give the couple the apartment they deserve?

Meanwhile Dom's investigation reveals that Stuart and Sarah are far from the only victims of this bunch of cowboys. He discovers that the company are making some misleading claims on their website and, as Dom tries to confront the builder in question, he discovers that he is a very difficult man to pin down.