All sorts of things tempt people every day and, while most cravings are quite benign -- a sugary treat or a new pair of shoes -- there are times when fixations evolve from the trivial to the terrifying. The latter are covered in "Dark Temptations," which presents actual cases of perverse fascinations that took deadly turns. Each hourlong episode features two stories -- re-enacted and interlaced with first-person accounts by survivors and perpetrators -- with commentary by psychologists, authorities and criminologists.