When Elsie Barson is found dead on the hospital floor, who should be surprised, or even care? 'It's probably a blessing,' says the ward manager.

Elsie was one of thirty late stage dementia patients on the elderly Challenging Behaviour ward, where nothing would surprise the long-suffering care staff. But Elsie's widowed husband is a retired police detective, and he smells a rat. Did Elsie fall? Or was she pushed? Who would do that to a harmless old lady, and why?

Unfortunately, Mr Barson is himself beginning to suffer from Alzheimer's. Will his failing memory prevent him from solving this mystery? Who will solve it first? Elderly Mr Barson, with his failing memory but a lifetime's habit of keen observation and meticulous note-taking? Or the hilarious bumbling middle-aged Detective Inspector Rae, who can never stop at mixing two metaphors where he could mix three? Or the audience?

Rob Gee has struck gold in conceiving this unique and compelling piece of one-man theatre.

The subject matter and the setting are unfamiliar and uncommon dramatic territory. There is still precious little good drama about the elderly in our society, compared with 'sexier' issues; but as long as medical science manages to prolong life but fails to conquer Alzheimer's and other types of dementias, these are issues we need to spend more time considering.

Rob's performance brings us into the world of elderly 'challenging behaviour' care as he experienced it as a psychiatric nurse in the mid 1990s. He says 'a great deal has improved since then', but I have my doubts – I suspect the reality in many institutions is still very close to how he depicts it (or worse – thinking of Winterbourne View).

He presents a wide range of characters (15, in all): residents, staff and the (sadly few) visitors, all distinct and credible. The story is mainly told through the eyes of two characters, each occupying one side of the stage: elderly Mr Barson, slowly and painstakingly collecting evidence and piecing the story together; and the careworker Dean, who is a wonderfully drawn character: referred to frequently as 'rather a tit', he describes himself as 'your socially inappropriate friend', he wouldn't even recognise the term 'politically correct', he alludes to appalling details of events in the hospital regarding them as all in a day's work but his heart is essentially in the right place.

The writing is superb. Rob Gee is now a performance poet, and some of the text of the play is pure poetry. Other parts are comic genius – from the mixed metaphors of the detective ('We've bitten off the wrong end of the stick and now they're dying like hot cakes') to the hilarious story of the police kidnapping a random bloke they have mistaken for a missing resident ('Of course he's upset, he's mental!'). I would like to put Elsie's prologue about dementia into the National Curriculum!

As befits the story of a community in its fading years, the pace of the performance is gentle and unhurried, with slow fades from scene to scene, allowing the audience plenty of time to absorb each new development. One clever aspect of this piece is that it can be performed straight through to fit the standard allotted hour for inclusion in a fringe festival; or, better still, like the performance at the Old Fire Station, the audience can have an interval between the conclusion of the investigation and the reveal to discuss the story and try to solve the mystery between themselves. The audience last night was spurred into keen discussion of all sorts of issues surrounding dementia, and could have gone on talking for hours.

Well done, Rob Gee. I hope this show runs and runs.