Lin Shaye continues to offer the best performances in the horror genre and The Last Key rewards her with a bigger meatier role. Even though the film detracts during the climax, it's able to overcome it by having a strong story.
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?"