A blood residue specialist leads police to the killers of an East Sussex waiter, brutally bludgeoned in his flat. And a forensic entomologist uncovers a case of extreme neglect when a Merseyside grandmother is found dead in her home.

When a teenager's body is located in a shallow grave, a soil specialist is called on to unearth evidence to convict the killer. And as a murder investigation on Merseyside stalls, a fibre expert is enlisted to revive the case.