A body suffering from head trauma found one morning in a store, near the safe, appears to have been the result of an interrupted robbery. A fingerprint found at the store connects the robbery in some way to a young girl kidnapped twenty years before. Sara and Warrick find themselves assigned to investigate a woman who burned to death while the house around her was hardly affected. Sara claims it's a case of mythical "spontaneous human combustion", while Warrick insists there is a simpler explanation. They compete to find the true answer.