The presence of a previously unmentioned childhood girlfriend—a first love named Tess—is just awkward, an obviously plot-driven obstacle put there so the show could stall Mike and Rachel’s inevitable reunion. Mike and Rachel simply aren’t an epic enough love story for the endless will-they-or-won’t-they device to work, and it definitely didn’t work here.
The worst thing is, Mike’s story doesn’t need it. Patrick J. Adams does wonderful work tonight, hitting all the right emotional beats—from denial to anger to utter desolation. To muddy this up with a love triangle for no logical reason other than to get to a predetermined end point isn’t great storytelling. Mike going into a downward spiral after his Grammy’s death is a worthy story arc—and it just might play out that way in future episodes—but in the context of this finale only, it’s pretty much a failure.