Detective Inspector Len Harper (David Threlfall) is called to 8 Coulthard Street after a body is discovered in the eaves by Michael (Russell Tovey) and his heavily pregnant partner Vidya (Amber Rose Revah) following a leak in the roof when they move into Flat 4. The body is of Melissa Young (Jessica Gunning) who hasn't been seen in more than two years, and isn't registered as missing, with no one even noticing her absence.

In his last week on the job before retirement, DI Harper is determined to unravel the mystery and discover the secrets behind the doors of Melissa's neighbours.

There are partners Elaine (Indira Varma) and Peggy (Victoria Hamilton) whose successful business and relationship is wrecked by the grim discovery. While Elaine never liked Melissa, Peggy is shocked and upset. But there is a dark secret connecting Elaine to the dead girl. Then there is divorced local newspaper editor Kieron (Steven Mackintosh) and his son Adam (Alexander Arnold). Just what are the personal secrets that Kieron's hiding? And finally maths teacher Joe (David Bamber) has lived in the house for 15 years. A stickler for rules and routine, he apparently lives alone, but it transpires that not all is what it seems in his basement flat...