Dom and Melinda investigate the work of a septuagenarian builder who has over half a century of experience in the building trade. Lawrence and Helen live in Berkshire with their three children. Wanting to give their girls a bedroom each, the couple remortgaged their property in order to pay for a two-storey extension on the rear of their house. Despite having paid £38,000 of a £46,500 quote, the family were left with an unfinished shell. Worse still, in the process of putting up the extension, the builder also managed to destablise the existing roof and carried out substandard underpinning work to the existing foundation causing cracks to appear in the rear area of the property. Melinda and her team try to fix the myriad problems with the building work. Meanwhile, Dom gets on the case of the builder responsible and discovers that his bad building habits have been going on for years. Putting the rogue under surveillance, can Dom catch him in the act?