Leonard, the hero of Christopher Nolan’s Memento, cannot form new memories. This poses something of a problem when you’re trying to find the guy who killed your wife. Her brutal murder is the last thing Leonard remembers, and he has been hunting for the perpetrator ever since. To survive in the present, he has a stack of Polaroids that he uses to identify friends and a carpeting of tattoos on his body, including the words JOHN G RAPED AND MURDERED MY WIFE draped across his collarbones. This is written backwards, so that he can read it every time he looks in the mirror. It is his purpose. It tells him who he is.

Because a human epidermis only has so much square footage, Leonard has to be ruthless about retaining only the information that serves his purpose, resigning the rest to the abyss. But the twist of Memento, when it comes, reveals more than the limits of a life defined by a quest for vengeance that will be forgotten as soon as it is achieved; it reminds us that memory can be treacherous, that history is narrative, and that sometimes, in the single-minded pursuit of justice, we do things we’d rather forget.