Kirstie Collins, who is helping Muriel McKendrick with the trial of a new drug, finds a severe adverse reaction from a patient, and wants to alert the drugs company, but McKendrick warns her against doing so. The staff of Darwin Ward, the cardiology ward, struggle to stop the spread of the life-threatening MRSA infection; suspicion about its origin falls on Nurse Julie Fitzjohn. There's gossip about Nick Jordan and Karen Newburn.