Rachelle Lefevre (Under the Dome) and Ian Lake (Rookie Blue) have joined the cast of Lifetime’s euthanasia-themed drama series Mary Kills People as series regulars for the upcoming second season. Mary Kills People centers on Mary Harris (Caroline Dhavernas), a single mother who is an ER doctor by day — but by night, she and her partner, a former plastic surgeon, moonlight as underground angels of death helping terminally ill patients slip away on their own…