Folau Fakatava showcased his class, dummy and all, leading the Magpies around in an 80-minute performance that will have been watched closely by his former employers in black.
But it was the injection from the bench of Lincoln McClutchie, Cooper Flanders and Kianu Kereru-Symes that sparked a Bay comeback in the final 20 minutes.
From 32-17 with 20 to play, it became 32-31 with 10 minutes to play - the Bay had suddenly given themselves a chance and Harbour were back-pedalling.
It was centre Nick Grigg who scored the match-winner with an ice-cool run into the corner, pinning the ears back after wing Ben O’Donnell launched a counterattack of his own after 74 minutes.
A late knock-on from Harbour allowed Hawke’s Bay to scrum their way through for a penalty and McClutchie completed the comeback.