Lifehouse — Spider Robinson

June Bellamy had gone for a walk in a park--and came back with memories missing. She didn't know that, but her partner could tell; she'd told his answering machine about strangers in the park.

Now June and Paul are on the run from insidious super-humans who, they fear, can edit their memories and track them down no matter where or how well they hide. They are desperate. But not nearly so desperate as their pursuers.