Something happened on the school trip.

One of the class has been replaced by an exact replica of themselves. At least that’s what everyone’s saying. Once a rumour starts, it can be difficult to remember what is real – or who. Convinced that there is an impostor walking among them, a group of teenagers is determined to root out the intruder. A mystery about friendship, the nature of truth, and humanity. When it comes to it, how do you prove that you are a human?