ne of the biggest thrills of screen detectives is the knowledge that you are watching someone much smarter than you. When Sherlock Holmes vanishes into his mind palace to stitch together dozens of ostensibly unrelated clues into an undeniable truth, or when Columbo doggedly wears down an exasperated murderer to the point of confession, it is comforting to see their expertise deployed with such ease. But such thrills aren’t for James McAvoy. For James McAvoy has just been signed up to star in My Son, where James McAvoy the actor has to solve a mystery without any help from anyone else. He will not be given a script. He will not be given any dialogue. In My Son, McAvoy will essentially just be dropped into a number of scenes until he can improvise his way to a solution. Admittedly, there is a plot to My Son. McAvoy will play the father of a missing son, who travels to the town of his ex-wife in a search for answers. It has also been done before, given that it is an adaptation of the 2017 film Mon Garçon. Nevertheless, according to the chair of My Son’s production company: “James will be doing the detective work of the film in real time, on camera, to create real tension for this thriller.” It is undoubtedly a fascinating idea. The rest of the cast (including Claire Foy, who will play the ex-wife) will provide the structure, being aware of the shape of the narrative, but McAvoy will be a loose cannon. It could be compelling. It may be brilliant. But, then again, it could stink. After all, the fate of the whole project seems to rest upon one question: what if James McAvoy is a crap detective? Honestly, what if he sucks? What if he couldn’t see a clue if it booted him in the shins? What if My Son consists of nothing but a succession of scenes where he repeatedly fails to miss a guilty glance, or a missing knife, or Foy covered in blood chanting, “I killed our son”, for 15 minutes straight, an inch from his face? Don’t get me wrong: I would still watch, but probably not for the reasons that the producers hoped. My Son is not a completely new idea. For a while, there was a minuscule fad for chatshows where the host was not told the identity of the guest ahead of time. Tig Notaro had one last year, and Mike Mitchell had one a few years earlier, and both were short-lived. This is because, if the host does not recognise the guest, the interview is awkward and stressful; and if they do it’s unprepared and unsatisfactory. But My Son has the potential to be so much worse, because the entire project could come crashing down at any moment. If he, say, declares that Foy’s mum abducted his son, and wrestles her to the ground three minutes, that does not leave the rest of the action with anywhere to go. On the other hand, what if My Son works so well that it marks a new way forward? What if TV shows decide to just throw an actor into the thick of it without any direction or lines? What if every new episode of EastEnders had a guy wandering about trying to work out why everyone was so miserable? What if Call the Midwife shoved a novice on to the set and told them to deliver a baby? What if someone had to appear on Westworld without any idea of what was going on? Their brain would explode after about 30 seconds. It would be great. Either way, My Son sounds like it will be a must-watch. And if that means watching through our fingers because it’s the most excruciating thing ever put onscreen, so be it.