Captain William Paris, Alastair Sim, has just taken on the role of entertainments officer at an army camp and is disappointed by the poor turnout for an evening of classical music. In a bid to lift morale, he heads to the local pub, The Rose and Crown, only to find it buzzing with soldiers—including his own driver—and he hatches a plan to try something more engaging.
With the help of Lady Dodds, Martita Hunt, Paris begins assembling a panel of local notables who can entertain and provoke thought in equal measure. The lineup includes the opinionated Professor Mutch, Colin Gordon, a popular BBC radio figure; his friend the oil painter George Prout, Roland Culver, and George’s wife Angela Prout, Elizabeth Allan. When Paris arrives at the Prout home, he interrupts Mutch and Angela just as they are about to share a private moment, a moment that hints at deeper tensions beneath the surface of a polite marriage. The panel is completed by the hard-of-hearing Doctor Hector McAdam, Miles Malleson, and the outspoken Labour MP Joseph Byres, Edward Chapman.
The brains trust begins under the careful coordination of Paris’s secretary, Private Jessie Killigrew, Janet Brown, and the hall fills with a curious crowd eager for wit rather than solemnity. Paris tries to steer clear of politics and religion, opening with innocuous questions about cows chasing trains and whether the Moon is inhabited. Yet the mood tightens quickly when Byres takes offense at remarks aimed at him and threatens a confrontation. A later inquiry about marriage, posed by Killigrew, exposes fractures within the Prout union and adds a personal sting to the proceedings, forcing Paris to call for an interval to restore order.
When the second half resumes, the room is packed again, and Paris attempts to nudge the discussion back toward harmless topics like bluebottles. But Killigrew’s insistence on answering her earlier question about marriage reignites the tension. The Prouts’ marriage comes under scrutiny once more, and Mrs. Prout drops a bombshell: the Professor is her lover. The gathering teeters on chaos until Paris abruptly closes the event, promising a return to the safe, familiar music of a string quartet next week. A soldier rises to applaud and asks if the brains trust could become a regular fixture, a suggestion that earns lingering approval.
Behind the scenes, concern for Mr. Prout grows as he disappears, only to be found back at his house, drinking heavily. The group follows and fears he might leap from the cliffs, but he is merely seeking a quiet moment to paint. The Professor’s selfishness is laid bare, while Mr. Prout begins to show more understanding and restraint, attempting to treat Angela with greater consideration.
The film closes on a paradoxical note: the string quartet plays again, and Paris sits in an almost empty theatre, the evening’s entertainment having stirred both energy and unease among the camp.
