Martin's first patients are Pauline's Uncle Jimmy and Aunt Jennie. They are trying for a baby but cannot conceive. Uncle Jimmy gets inexplicably angry with Martin. Martin sends them to Truro so Edith, who is a fertility specialist, can assess them.

Louisa applies for a teaching post at the local school, and is interviewed by the new Headmaster. She gets the job, but notices that the Headmaster is acting strangely. He has an arm that rises up into the air without him seeming to notice it.

Martin's Aunt Joan is scathing of Martin's attitude towards Louisa. But when Martin tries to talk to Louisa, he can't help himself and angers her with his old-fashioned views.

Louisa also has a frosty encounter with Mrs Tishell, who disapproves of her. The Headmaster comes to see Martin about his constipation, but starts acting in a paranoid manner. Martin notices the Head's strange physical behaviour for the first time, but before he can complete his examination, the Head rushes from the Surgery.

Uncle Jimmy's test results come back showing he has dangerous levels of testosterone in his blood, and after initial anger, Jimmy makes a tearful and surprising confession to Martin.

Louisa goes to hospital for a routine check-up and discovers that Edith is going to be her doctor. Louisa learns something about Martin and Edith's relationship during medical school that shocks her.

Louisa returns to her school and discovers that the Headmaster has taken her pupils down to the treacherous rockpools of Roscarrock Cove for a nature walk. Quickly finding the children and attempting to alert Martin via her mobile, Louisa soon finds herself in danger.