With the Kings winning the first three meetings, success here would have confirmed them as champions but instead they slipped to a 3-1 defeat.
The game was scoreless after two evenly matches periods before warming up in the third.
Patrick Elias gave the Devils the lead for the first time in the series when he broke the deadlock only for Drew Doughty to draw the Kings level a minute later.
Adam Henrique restored the advantage with four-and-a-half minutes to play and in the dying seconds Ilya Kovalchuk netted to ease any tension.
Game five takes place at the Prudential Center on Saturday, with the Kings again looking to the secure the cup.