Francis Bigger is a charlatan faith healer who convinces attendees that mind over matter is more effective than medical treatment. He suffers an accident during a lecture and is admitted to the local hospital, where he quickly requests a private room after meeting a ward full of eccentric patients: Charlie Roper, a bedridden layabout who fakes symptoms to stay in hospital; Ken Biddle, recovering from an operation who makes frequent trips to the ladies’ ward to flirt with his love interest, Mavis Winkle; and Mr Barron, whose mind has declined after news his wife is due to give birth to their first child. During Bigger’s stay, he also crosses paths with the clumsy yet charming Dr Jim Kilmore, who is popular with patients and loved from afar by the nurse Nurse Clarke. The hospital atmosphere is lively and sometimes volatile, with everyone watching to see how the new arrival will fit in.
The day after his admission, Bigger meets Dr Kenneth Tinkle, Kilmore’s superior, who is detested by the patients just as is the battleaxe Matron Lavinia, the stern authority who oversees the wards. Shortly after Bigger’s arrival, a novice nurse arrives: Sandra May, who tells Clarke that she plans to meet Tinkle to repay him for saving her life — though in truth she was only treated for tonsillitis. After a shift, May heads for Tinkle’s room to profess her love, breaking hospital rules that female staff are not allowed in the male quarters. Tinkle cruelly rebuffs her, only to find himself caught in an awkward moment with Kilmore and Matron. Fearing for his position, after May and Kilmore depart, Tinkle teams up with Lavinia to cover up the truth.
An opportunity soon arises for Tinkle to be rid of Kilmore. The young doctor spots May going onto the roof of the nurse’s home and believes she is about to commit suicide, unaware she only intends to sunbathe. In trying to rescue her, Kilmore creates an embarrassing scene that fuels claims of sexual impropriety against him. A hearing with the hospital governor sees Kilmore attempt to reveal the truth, but Tinkle and Matron deny the accusation, revealing that May has since left. Nurse Clarke knows what really happened on the roof. With his reputation in ruins, Kilmore resigns, prompting Clarke to tell the male patients what she knows.
Roper, disgusted by what was done to Kilmore, rallies the ward to seek revenge on Tinkle and Matron, with Bigger and Mavis enlisted to help the women. A nocturnal mutiny unfolds as the men and women take control of the ward: Sister Hoggett is briefly subdued to prevent alerting the orderlies, and the group brings Bigger along, who, after mishearing a conversation between Tinkle and his assistant, believes he is dying and decides to marry Chloë Gibson. The gang captures Tinkle and Matron, and the women force a confession from Matron by making her endure a blanket bath, while the men threaten Tinkle with an enema to extract his confession.
The next day, Kilmore is appointed the new hospital registrar while Tinkle is reduced to a simple doctor. Mr Barron, now fully recovered, leaves with his wife and their new baby. Meanwhile, Bigger prepares to leave the hospital with Chloe, but he resents the bickering he has endured and the need to give up his work as a faith healer. On the way out, Bigger deliberately falls on the steps and injures his back again. As he is brought back inside the hospital, he breaks the fourth wall to tell the audience that he hopes he will be staying for a long time.
