Nice rapid­ly turns to naughty in this Christ­mas-set black hor­ror film. “Home Alone” meets “The Bad Seed” in “Bet­ter Watch Out,” a clever black -cum-hor­ror pic in which the appar­ent home inva­sion that traps a babysit­ter her charges turns out to be some­thing else entire­ly. This macabre […]