Annie's involvement in a murder case results in conflict with her father. Briggs finds it hard to be a good husband, while Susie continues to anger a lovesick Swift.

Events end up taking a sinister turn after DI Sawyer’s missing suspect makes a sudden violent reappearance. Coulson recruits Fenton to do his dirty work. Annie and Tommy try and play cupid to Susie and Swift.

Coulson decides to Briggs’ misfortune to reassert his power at the police station. DI Sawyer questions a suspect with a shocking wartime story to tell.

A tragic event leaves the the team having to decide where their loyalties lie. Time is running out for Annie and DI Sawyer as they find it hard to unlock the dark secrets of the Petra Project.