Remember the Lost » L. Dunbar [3]

After the painful fight with the Dread Doctors, Ella and the pack try to finally relax as their school year is almost coming to an end. But things in Beacon Hills never stay calm. After a little boy turns up alone, the pack discover a new threat that erases people from existence. When the pack can't remember the few friends that were taken by the hunt, everything in their lives change, and suddenly Ella and Liam no longer exist. It's just only Liam.