Every parent has thought this: did my creepy-looking son stab and kill that boy found dead in the park? Even though Santa was watching? You’d hope not, and thus the intrinsic conundrum of the narrative is set. Captain America can’t work it out, and he vacillates between believing his progeny is guilty or innocent. Based on the eponymous novel, the story moves back and forth in time, tantalising us with new details and building to a tense climax. Someone’s getting a detention…or maybe not.