Who the Eff Is Annabelle? 7 Theories About Cruel Summer's Latest Mystery

If it's not Kate with DID, maybe it's Martin? Let's look at the facts here. Kate told her therapist that Mr. Harris "came downstairs right before I (she) was rescued, and something was different. Something was wrong. And that was when I met Annabelle." Could Annabelle be Martin's alternative personality that was different – menacing – than his usual charming demeanor?

One fan theory on Twitter proposes that maybe it was the trauma of his sister killing herself (and not his dad) that fed into the origin of Martin's "Annabelle." "So he is trying to save Kate from the adults in her life who are letting her down," she adds. This probable backstory is giving me major House at the End of the Street vibes.