What do you keep in your potting shed? Trays of neatly bedded seedlings? Defunct household gadgets that you hope to throw away one day? Or a dark and deadly secret that has ripped your family in two?
For the Callifers, the family under scrutiny in Graham Greene’s rarely performed 1958 play, it is the latter. Something nasty happened in the potting shed several decades ago and now no one who can remember it will talk about it. Meanwhile James, the man at the centre of the incident, can’t remember a thing, and his mental health is collapsing as a result. He turns up at his father’s deathbed to extract the truth, but his tight-lipped mother won’t let him into the bedroom and the old man dies without healing the rift. James, now desperate, turns sleuth and tracks down the family black sheep for an answer.

The black sheep here is a Catholic priest – not a disgrace for most families, but the Callifers are devout atheists. And, as the play peels away the layers to arrive at the secret, it becomes clear that the conflict between atheism and religious faith is at the heart of the matter. The play has the appeal of any psychological thriller: you want to know what happened. And Svetlana Dimcovic’s fine production, nicely framed in a series of quiet 1950s interiors, keeps the tension well and makes gripping work of the big revelation scene, with Paul Cawley as James, sweaty-palmed and shaking, holding the stage.
Martin Wimbush impresses too as the priest whose intervention in the events in the potting shed cost him his faith and have left him trying to fill up the empty space with whisky. Zoe Thorne is strong as James’s astute teenage niece, who is determined to ferret out the truth, and David Gooderson is touching as James’s compassionate psychoanalyst.
But the subject matter seems too big for the play: the catastrophic event, once revealed, seems improbable and poor ground for real debate. Meanwhile the psychological effects of spiritual conflict and doubt are not explored in enough depth because the play spends more time arriving at the revelations than examining their impact. Most unconvincing is the damaged relationship between James and his ex-wife. A quietly gripping production makes this an interesting evening, but the play smoulders rather than blazes.