Wastwater *** TNT

This “elliptical triptych” is well acted, sympathetically directed, faultlessly designed and promises much more than it actually delivers. Taking its title from England’s deepest lake, Simon Stephens’ new play intimates hidden secrets and dark dealings.

Certainly the mood becomes increasingly threatening as the evening progresses. Linked by location (the edges of Heathrow Airport, the dialogue punctuated by the drone of overhead aircraft with their promise of new adventure) and, tenuously, by reference to characters in common, these three short playlets are, in themselves, confidently written. Frustratingly, they leave too many questions unanswered.

In the first, serial foster mum Frieda (a convincing Linda Bassett) says goodbye to Harry, her favourite, before he flies off to Canada and a life without her. Next, art teacher Mark has a tense hotel room encounter with older, married police officer Lisa whose sexual tastes are way beyond his comfort zone. Finally, a chilling meeting in a deserted warehouse between manipulative, child trafficking Sian (another of Frieda’s foster children) and Angus Wright’s cowering Jonathan (who once taught Mark) leaves one uncomfortably uncertain as to his motives.

Katie Mitchell’s direction ensures that each scene holds the attention, and Lizzie Clachan’s design provides a trio of completely different sets in not much more than the blink or two of an eye. But Stephens offers both too much and too little in these rather pessimistic snapshots which never quite add up to a complete picture.

Royal Court Theatre, Sloane Square, SW1W 8AS (020 7565 5000) Tube: Sloane Square royalcourttheatre.com Until May 7 £10-£28