Hugh Laurie stars as acerbic but brilliant New Jersey medic Dr Gregory House in the fourth series of the Emmy- and Golden Globe-winning medical drama. This week’s seasonal episode sees House battling to diagnose a mother with paralysis in her hands. Scornful of the woman’s claim that she never lies, the medic searches for a way to prove she is dishonest.

Christmas at the Princeton-Plainsboro Hospital finds House and his team tackling the case of Maggie (Janel Moloney, ‘The West Wing’), a 34- year-old mother with paralysis in her hands. A series of experts have failed to diagnose her condition, but House wastes no time in jumping to his usual conclusion that the patient is hiding something. He is especially irked by Maggie’s insistence that she always tells the truth – even to her 11-year-old daughter, Jane.

House rifles through Maggie’s medical history in search of something out of place, but only turns up the information that she underwent a double mastectomy several years ago. 13 challenges him to accept the fact that Maggie is telling the truth, but House cannot shake off his suspicions. “There’s a reason that everybody lies – it works,” he says. “It’s what allows society to function.”

The team races through a series of possible diagnoses, including cancer, drugs and STDs. When Maggie suddenly loses her sight, the doctors launch another battery of tests, while House searches the patient’s computer for clues as to her health – all to no avail. “We haven’t found anything abnormal on any test,” Taub reports.

House then hits on the idea that Maggie has a psychological ‘conversion disorder’, whereby her brain thinks there is something wrong with her body. “Her mind is tricking her body,” he says. “We need to trick her mind.”House’s proposal is to treat Maggie with a placebo and have Jane lie to convince her that the medicine is working.

However, the strong-minded Jane refuses to trick her mother, and the plan is scrapped altogether when Maggie develops swollen lymph nodes in the throat that prevent her from breathing. “Swollen lymph nodes means it wasn’t psychological,” House says.

Bleeding in Maggie’s eyes sets off a new round of diagnosis, until House decides the only way to solve the puzzle is to conduct a bone marrow exam. Chase begins to bore into the patient’s bones, only to encounter massive friction. “The bones are harder than the drill!” he declares. The doctors are forced to conclude that Maggie has osteopetrosis – a hardening of the bones.

The bad news for Maggie is that nearly all types of osteopetrosis are incurable. While the team runs tests to determine which variant she has, they search for possible bone marrow donors who could help her – starting with Jane. However, Maggie is adamant that her daughter should not be allowed to donate marrow. Her determination prompts House’s curiosity – and leads to a surprising revelation. But his insight amounts to nothing when tests confirm that Maggie’s osteopetrosis is untreatable. “Who’s going to tell the patient she’s dying?” 13 asks. But is the prognosis truly fatal, or can House achieve a genuine Christmas miracle?

Also this week, House laments the lack of competitiveness in his team now they are safe from elimination, so he decides to inject a little tension by organising a secret-Santa exchange. “I’m trying to drive them apart,” he says. “With gift-giving?” Wilson replies. House quickly outlines his plan – but neglects to mention that there is only one name in the hat...