Not long after, Backlund's shot beat Holtby but not the post, however the forward was high-sticked by Boeser on the play putting Calgary on another man advantage, this time for four minutes.
They finished the middle stanza with another powerplay but were 0-4 after 40 minutes of play.
The Canucks scored their second of the night on the powerplay in the third, Tyler Graovac beating Markstrom at 2:30, before Boeser added another PP marker at 7:47.
Then it was J.T. Miller scoring short-handed at 11:28 to pull his side within one.
Not long after, Horvat was sprung on a partial breakaway but Markstrom made the stop.
Boeser then tied it up with 2:02 to go.
Dube drove in with less than minute left, Holtby making the first save but then Dube got the rebound and drove behind the net for a wraparound that the Vancouver 'tender managed to get his toe on to keep it knotted at five and force OT.