A journalist once had cause to ask why Frank Sinatra was sitting backstage without any trousers. The singer pointed at the hack's crumpled suit and replied: "So I don't go out with my pants looking like yours." Fiona Evans's play finds Frank with his trousers round his ankles, though not in his dressing room in Las Vegas but the frozen food aisle in the Whitley Bay branch of Morrison's. Geordie has had a long career as a Sinatra impersonator, but recently he's begun to forget the words. In fact, he's begun forgetting everything, including whether his wife, Vera, has left him, or whether he is actually married to Ava Gardner.

A recent NHS review predicted that cases of dementia could rise by 72% over the next 20 years. It's a hugely topical and harrowingly difficult subject to broach on stage, yet Evans succeeds in making us party to Geordie's hallucinations. To his family, he's a confused, vulnerable, obstinate old man, while in his own mind he's still chairman of the board. The action is subject to a tortuous back-story that would, frankly, leave anyone confused, yet Evans's compassion for the central character is keenly felt. The cruelty of the disease is summed up by Geordie's daughter (a touching performance by Heather Saunders): "I adore this man – I only realise how much now that I'm losing him."

This is the first time that Live and the Stephen Joseph Theatre have collaborated – and the partnership looks a strong one. Choice selections from the great American songbook are delivered with real panache and no little poignancy by Anthony Cable, whose performance is, quite literally, all mouth and no trousers.