Tom Watson is having a normal day at work. His job is to inject fish from the lake with an antibiotic serum. He accidentally injects his thumb with some of the serum. The next day, Tom feels great. While at the lake, he puts some of the serum in his tea. He starts to get a headache, then hears voices in his head. The fish are talking to him, asking him to stop injecting them with serum. They tell him to call for help by concentrating. Tom does so, and falls asleep. The Doctor examines the tea in the TARDIS. He works out a formula to block the side effects of the serum.