Guy is taken hostage and forced to hold a live grenade while the hospital is evacuated. The grieving husband of a deceased patient blames him for his wife's death and wants revenge. Will Fletch have to sacrifice himself to save Guy? Ollie and Zosia's feelings for each other are brought into sharp focus when they're placed in a life-or-death situation. Dom thinks he's being tested when Hanssen gives him a tricky patient to deal with - a man who is already suing his last doctor.