Now Is The Hour, Hill Street Theatre, Edinburgh

You may associate it with Gracie Fields, but "Now Is the Hour" is adapted from a traditional Maori song. So it's a masterstroke to have it sung here by a young New Zealander serving as a Royal Navy pilot. When the song is heard in David Walter Hall's play, it is scarcely possible to hold back a tear.

The year is 1942 and the liner Laconia has been torpedoed in the Atlantic. For 28 days, a band of survivors struggles to stay alive in a lifeboat. They include Peter Medhurst and the married Scot "Catriona" (renamed to conceal her identity), who is carrying his child and to whom, in her final hours, he croons, "soon you'll be sailing far across the sea". In mimed, dreamlike flashbacks, we see the emergence of their affair, the ship's destruction, and the hours of hope and despair.

The idea for the play came from producer Peter Christopherson, who, as Medhurst's nephew, came into possession of his uncle's letters. Of the three survivors, it is Doris Hawkins (sensitively played by Catherine Cusack) who frames the story in a letter to Medhurst's mother.

The acting of the 11-strong company is convincing enough, on a versatile set – a fractured lifeboat on a shiny floor against a marine backcloth. The incident is soon to be dramatised by Alan Bleasdale for BBC television, but it's unlikely to have half as much heart as this poignant production.

To 25 August (not 13, 20) (0131-226 6522)