If youve been in Edinburgh for a few weeks, or even days, you will probably have experienced the Evening with Dementia marketing campaign, which consists of actor Trevor T. Smith staggering along the Royal Mile, shaking and gap-toothed, with a large placard for the show strapped to his back. You might also have seen him pasting pictures of himself to the Miles poster pillars. Character advertising in the street can be tedious, but I found Smiths technique distressing and even a little crude. However, I was greatly impressed by his show, and its sensitive depiction of the mind of a man with dementia.In the ordinary world of his nursing home, this nameless man hardly speaks at all, but opens up to his audience in a flood of eloquence. After all, as he repeatedly tells us, he used to be an actor one who always wanted to play King Lear. But, of course, now that he probably could, he wouldnt be able to find the theatre.Smith, the real actor, nuances his performance brilliantly, so that fifty minutes whiz past in the company of his endearing, intelligent and amusing character. The man reflects with humour on his situation: it is always too hot in his nursing home; Christmas is the worst time of the year, because a different group of singers come in every day, singing the same and the same carols. The familiar, familial question what have you been doing? is a stupid one, he reflects, and claims that answering such questions or those you dont know the answer to with pardon is always a good wheez.There is a deeply moving element to Smiths script too. For all his bravery in the theatrical private world, the real-life man lacks such bravery, or the ability to show it when he cant remember the words to express himself. In a moment of insightful clarity, Smiths character is desperate: my brain is like a bird that has lost all its feathers. Smith explores the idea of human parabola: that elderly people become like babies. Whilst the man claims, surely rightly, that being old is no fun compared with being young, he does recount meeting a baby and a thought striking him: there wasnt a memory between us.Smith performs an often excellent script with verve. Things become a little trying when we enter a section on the demented nature of society as a whole; the old man claims that the world has forgotten how to be humane. It seems a trite, unnecessary strand in an otherwise exceptional one-man show. Dont be put off by the advertising: An Evening with Dementia is moving and inspiring.