Barton Street Sgt. Nikki Wright comes across a man with stab wounds on the shoreline of the river Thames. Meanwhile, Stamp and Hemmingway are on the trail of two armed robbers who have just held up a bookies' headquarters at gunpoint. In the ensuing chase, the getaway vehicle comes face to face with an ambulance carrying Sgt. Wright and the stab victim, resulting in a pile-up and a standoff between the gunman and armed police. As Wright manages to calm the gunman down, the second robber manages to flee to safety, and the chase is on to find him before he strikes again. However, Meadows soon realises that a supposed hostage may have secretly been part of the robbery.