Bo Horvat gave the Islanders a 1-0 lead on the power play at 14:32 of the first period. Mathew Barzal faked a shot atop the left circle before finding Horvat, who buried a one-timer from the slot past Primeau’s glove.
Kyle Palmieri extended the Islanders’ lead to 2-0 at 16:58, beating Primeau high blocker side from inside the right dot.
Caufield pulled the Canadiens to 2-1 at 19:56 on the power play, scoring from a sharp angle after his centering pass was blocked and the puck bounced back to him.
Mailloux tied the game at 2-2 when he beat Varlamov glove side from the slot 59 seconds into the second period. From the left corner, Jake Evans found Mailloux alone in the slot.
The Islanders could not score on a power play in overtime and were 1-for-6 on the man-advantage for the game.
“There was a lot of drama in that game,” Islanders coach Patrick Roy said. “It was 2-0, and they tied it at 2-2 in the [second]. We had plenty of power-play chances to seal the deal. Both teams were fighting back and forth, and they tied the game, and we had our chances 4-on-3. We hit the post in overtime and one in the shootout. It was a hard-fought game for both teams. I don’t know if it was an exciting game for you guys and the fans, but it was exciting for me.”
NOTES: Islanders forward Anthony Duclair left the game at 3:19 of the third period. He could not put weight on his right leg after getting tangled in the slot. There was no update following the game. … Caufield has five goals in six games. … Canadiens forward Nick Suzuki has points in four straight (five assists). ... Dobson has four assists in five games.