When Major Len Miller is found dead at the bottom of his stairs, a bloody fingerprint implicates his grandson; as David and Vivienne shed light on a dark secret from the major's past, they also must deal with the fallout from their indiscretion.

After young medical student Japesh Patel is stabbed to death, Billie wonders if it's connected to a similar, non-fatal attack on a gang member. Meanwhile, tensions between David and Vivienne reach a breaking point.

A delivery driver is killed, and a trace of his movements places him at a pub that his wife frequents; she has a motive, but she's an alcoholic and can't remember if she killed him or not; when David doesn't turn up for work, Vivienne confronts him.

A boxer confesses to killing her manager, but the detectives think she may be covering for her father; when a suspect accuses David of planting evidence, he's devastated to realize the team has doubts, and he makes a decision about his future.