The case of two young women shot dead in a house basement forces Jack to lock horns with an old flame, the ambitious DI Chrissy Reed. As the pair's animosity rapidly escalates due to their conflicting motive theories and failure to ID the victims, Nikki's probing unearths the potentially career-damaging truth behind it. Meanwhile, Leo wrestles with providing a second post-mortem on a baby suspected of being abused and smothered to death by his mother, Shona. The father, Mark, is adamant she is innocent. He pleads with Leo to find an alternative cause for their son's fractures and death to free his wife before their other son, Darius, is adopted. However, Leo soon realises that to achieve this he must re-examine the work of his pathologist friend, Richard Fell, and prove he made a mistake in his evidence against Shona.