It"s been a year since Martin resigned his medical license, and Louisa is now the one seeing patients out of the surgery for her child counseling practice, while Martin looks after James Henry and four-month-old Mary Elizabeth. When the mother of one of Louisa"s patients presents with serious symptoms but refuses to allow Martin to examine her, he finally admits that he wants to be a doctor again.

The Portwenn surgery has reopened, but between Martin and Louisa sharing the office and a less-than-competent new receptionist, things aren"t running very smoothly. When Louisa"s childhood dream home goes on the market, she jumps at the chance to look for a larger space. The house"s owner is an accident-prone recent widower who seems haunted by his wife"s death—perhaps literally.

While checking on a sick sheep farmer, the Doc runs into Stewart James, a patient who used to suffer from delusions that he lived with a giant squirrel. Stewart is now starting a survival course business, and he invites Al and PC Penhale to join him in the woods for a test run. But when Stewart begins to behave oddly, Al worries he"s having a mental breakdown and must figure out how to get help.

When Martin advises a patient suffering from migraines to stop cold-water swimming, Mrs. Tishell"s attempts to help almost lead to disaster. Martin has his own headaches to deal with when an herbalist sets up shop in the village and then an ex-flame arrives on his doorstep, inviting him to speak at a medical conference in London. Meanwhile, Penhale tries to rekindle his romance with Janice.

Louisa is shocked when her father, Terry, makes an unannounced visit. After it becomes clear Terry is unwell, he agrees to let Martin examine him—but that backfires on the Doc, who is now bound by the rules of medical confidentiality. Ruth employs an unconventional method to test Martin"s blood phobia, and Bert tries to get a squatter to vacate his trailer park.

Martin and Louisa travel to London so he can deliver the keynote address at the Imperial College Obstetrics Conference. All does not go smoothly, however, as Martin is accidentally headbutted while saving a choking woman, and then his ex-flame Sophie causes a scene at the cocktail reception. Back in Portwenn, Penhale proves to be both a hindrance and a help to Janice as she babysits the children.

The news of Martin"s invitation to be the dean of Imperial College spreads through Portwenn like wildfire, before Martin and Louisa have even decided whether he will take the job. Mrs. Tishell and Penhale are crushed, while Morwenna questions what she wants to do with her life. Can the villagers cope with the Ellinghams" ultimate choice?

As the Ellinghams prepare to leave for London, Ruth admits to Martin that she"s been writing a paper on his blood phobia, and she thinks he"s been misdiagnosed. Ruth is also counseling Mrs. Tishell on how to overcome her obsession with the Doc, while Penhale anxiously arranges their goodbye party. But when Chicken the dog escapes, Martin has a life-threatening accident trying to catch him.

Portwenn is full of festive cheer—until Martin tells Leonard that he needs to stop playing Santa while he awaits the results of his medical tests. Leonard decides to show "Doc the Grinch" the magic of Christmas, with unintended consequences, and Louisa works to arrange a Christmas parade through Portwenn. After a mishap, Martin confronts some of his fears and tries to embrace the holiday spirit.