While his recent film Split might not have got the critical acclaim that director M. Night Shyamalan would likely have wanted, it did showcase McAvoy's remarkable versatility, showing him playing multiple roles, sometimes within the same scene.  

Now, McAvoy has taken on another challenge. This time he's learning the plot of the movie he's starring in as he goes along, and with no lines to help him understand the subject matter better.   

The trailer describes My Son as a 'ground-breaking filmmaking achievement where both actor and audience uncover the mystery at the exact same time'.

Sounds interesting, right?

McAvoy plays the role of father Edmund Murray - he's someone's dad, not a priest - who gets a call from his ex-wife - played by The Crown star Claire Foy - telling him his seven-year-old son is missing.  After a while, it becomes evident that the child has been kidnapped, and it has something to do with the work that Murray does. 

Speaking about his role, McAvoy said: "I hope we'll give the audience something really tangible that they can hang on as this thriller rattles on." 

My Son is actually a remake of a French film of the same name - well, it's called Mon Garcon - and the leading actor in that, Guillaume Canet, wasn't provided with a script before getting stuck into that, either.bThe film was directed by the same bloke, too. Christian Carion was at the wheel for the French version and returns for the English remake.