Webb witnesses a drug deal on his way to work, but when he confronts the buyer, he discovers that he was actually buying several steriles of hospital-grade morphine. Meanwhile, whilst out on patrol, Casper and Fletcher find a man collapsed in the street, and soon discover that he has overdosed on a similar sample of morphine to that found by Webb earlier. As Perkins discovers that a quantity of morphine has disappeared from the pharmacy at St. Hugh's hospital, Webb pressures the dealer to give up the name of his supplier, but the breakthrough comes when Casper identifies a woman caught on CCTV outside the dealer's house as a hospital sister that he questioned earlier in the day.
