Sheahan put the Red Wings on the board and cut the Canadiens' lead to 2-1 with his sixth goal 1:28 into the second period.
Desharnais restored Montreal's two-goal lead with 8:57 remaining in the middle period on his 14th goal.
Plekanec's two goals gave Montreal a 2-0 lead in the first period.
He opened the scoring 7:49 into the game, then got his 20th goal with 5:49 left in the opening period.
NOTE: Detroit RW Tomas Jurco returned after missing seven games with a broken rib. ... Montreal LW Travis Moen missed his second game with a concussion. ... Red Wings C Pavel Datsyuk, who has missed 13 games with a sore knee, is skating but there's no timetable for his return. ... Detroit C Henrik Zetterberg, who had back surgery on Feb. 21, won't be cleared for contact until April 18-19. ... Pacioretty played college hockey at the University of Michigan. ... Montreal D Mike Weaver played college hockey at Michigan State. ... Canadiens' RW Dale Weise missed his second game with an upper-body injury.