What it's about:
Dr. Elise Rainier, the brilliant parapsychologist, faces her most fearsome and personal haunting yet: in her own family home.
What the critics thought:
The Insidious timeline is becoming so murky, even a scary ghost lurking behind a locked door in the basement might give up and say, "Time out! Am I even supposed to be in this particular story? Who am I haunting again, and what's my motivation?" - Richard Roeper, Chicago Sun-Times
The fourth installment of Leigh Whannell's ghost-and-mediums horror series wraps up its own free-association illogic with an impenetrable tangle of woo-woo spirit-world mechanics and lingo. - Emily Yoshida, New York Magazine/Vulture
Of the four Insidious films, only one has been any good and, although The Last Key may not be the worst of them, it's easily the most irrelevant and generic. - James Berardinelli, ReelViews
Insidious: The Last Key manages to unlock some humanity and tragedy from a well-worn narrative and revive a meandering franchise while bringing it full circle. - Don Kaye, Den of Geek