At a park, Annie was drinking water from a foundation. Just then, black goo sprang out and entered Annie through the mouth. Annie turned off the tap and wiped her mouth, looking uncomfortable. She then began to convulse and shortly after the Leviathan gained full control of her body.
Annie remained possessed throughout the Leviathan's appearances. Her form was shapeshifted into that of Dr. Gaines since the Leviathan disliked her lack of knowledge and immaturity, pointing out to Edgar that she didn't even know where babies came from.
Annie was killed when the Leviathan leader, Dick Roman, ordered this Leviathan to commit suicide by bibbing, aka eating himself. Nothing was left of Annie's remains.