Five-year-old Julie Harris goes missing after being seen playing at the local playground. Suspicion immediately falls on Julie's mother's new boyfriend, Peter James. But when her body is found inside a sewage pipe, evidence points towards local misfit Michael Dunn.

When items relating to the case are found in Dunn's flat, Walker has no doubt that Dunn is responsible. However, when it's revealed that a frantic young officer who found Julie's body planted evidence, Dunn's trial is thrown into jeopardy.