Part 1: When five-year-old Julie Harris goes missing from the playground of a public housing project in East London, the police launch a desperate search that brings results too late. DS Michael Walker joins DI Pat North in the subsequent murder investigation. They target Michael Dunn, a disheveled, unemployed alcoholic who lives in a squalid flat in the neighborhood. Although circumstantial evidence against Dunn mounts, the police still lack a crucial link between him and the crimeeven as the case nears trial. (Part 1 of 2)