[8] Mel Gibson headlines this M. Night Shyamalan (The Sixth Sense, Unbreakable) sci-fi thriller about a single father (Gibson) of two young children and his younger brother (Joaquin Phoenix) who discover mysterious crop circles in their fields. Signs unfolds like George Romero’s Night of the Living Dead, depicting a global nightmare — in this case, alien invasion — from the claustrophobic perspective of one family …