Nursing his terminally-ill wife, Det Insp ""Jack"" Frost's life becomes more stressed when, during a missing-child investigation, he unearths evidence on a 30-year-old case involving a skeleton chained to a locked strongbox that turns out to be empty.

Frost is invited to join fellow George Cross recipients in London. He is instructed to enlist the aid of WPC Hazel Wallace as a decoy to catch a serial rapist, but it exposes her to serious danger.