I'm trying to fill a psl or two, especially the idea I put below under a cut tag. All the details here. Between the ideas there's a mix for potential for body manipulation, kidnapping, unconventional forced surrogacy through science or technology, mental manipulation, possessive behavior, and possible alien possession or other. It really just depends on what's figured out in brainstorming.
The creature had spent a long time roaming earth. Its memory had started to go, and it couldn't even quite remember where it came from in the first place. Space, vampires, shapeshifter... it didn't know what it was and it didn't really care anymore. Life had become boring. It had yet to find any being that wasn't a regular human or animal in a very long time.
That changed when it found Audrey. A normal woman in general appearances, but somehow she's different. The creature knows its end is coming, so it sheds its form and lets its consciousness go into the body of a would be stray person it runs into on a back street.
But when the person wakes up, all they have to go on is a wallet. The bulk of their memories are gone and they have no idea what caused it or that the creature fused with them. James/Amelia quickly discovers that they're a multimillionaire, a thing set up by the creature before its death. They're retired and have a private island...
And are inexplicably drawn to Audrey. Audrey seems to be in a troubling situation, heavily pregnant, alone, and nervously trying to hide from someone. With the thought that Audrey might hold the key to some of their missing memories, or she might just be someone to help, James/Amelia offers to and takes Audrey to their private island. It's there that the mysteries that were hiding in the dark can be brought to light.