'F*ck the milk of human kindness. Welcome to the abattoir.'

This is a dark evening and BT's 18+ guidance is apt. It's also unmissable. Exceptionally assured direction by Alexander Hartley is combined with strong casting, and superb performances.

Philip Ridley's gift for savage prophecy is brilliantly realised. Set in the East End in one shabby room above a disused fur factory, inhabited by screaming birds, birthday party preparations for the evening are almost complete.

While birthday boy Cougar (Jack Morris) lounges around in his underpants and sunglasses looking at porn mags, his devoted flat mate Captain Tock (Max Reynolds) brings in the birthday cake and vodka.

While Cougar is forever 19 years old, Captain is bald and ageing. Captain's patient efforts are rewarded by insults, the most painful being cast as an unwilling yet complicit accessory to a party which is merely a lure. It is also a trap to allow Cougar to seduce Foxtrot Darling, a 15 year old schoolboy (Emily Smith).

Captain may initially be a party planning pimp, but he's appalled by Foxtrot's juvenile status, and piqued by Cougar's intent. He knows all Cougar's hot buttons, and which not to press. Merely alluding to youth-obsessed Cougar's real age causes Cougar to fly into a rage. Only their decrepit landlady Cheetah Bee (Alexandra Atkinson Snow) can calm him.

'I am at the end. You are at the beginning', Cheetah Bee intones, as Cougar writhes on the floor in a foetal position.

No place has been laid for Cougar's nemesis, Sherbert Gravel (India Opzoomer). While Cougar has set a net of lies to entrap Foxtrot, she has brought a bag of tricks to the party to set off some truth flares.

Foxtrot's confusion and vulnerability is played on by all parties. His bravado is offset by his school uniform – but his seduction is hardly non-consensual. Sherbert's spirited claim on him, and bold calling of Cougar's many deceits provokes an explosion of violence.

In a chocolate box of toxic cruelties, humour and compassion strike brief flames in the darkness, inhabited by predators immune to cruelty in the cause of beauty and youth.

My only misgiving was the casting of a girl as Foxtrot in a gender bending dimension which gave the actor and audience an unnecessary hurdle to leap.