Imagine a murder mystery where all the characters are animals. On Animal Crime Scene, David Attenborough investigates the mysterious death of a caribou in Alaska. There are plenty of killers in the frame and each has a characteristic way of despatching its victim - wolves rely on their cunning, giant bears have freakish strength and eagles use their stiletto-like talons. But none of the facts seem to fit the evidence.As the story unfolds, it is clear that the snow and ice is hiding a sinister secret. This is a wildlife murder with a real twist in its tail - but will you be able to guess the identity of the arctic assassin?