Missing

"Missing" is a young adult horror novel by R.L. Stine about two siblings, Mark and Clara, whose parents disappear one night without explanation. When the police fail to take their reports seriously, the situation escalates when Mark's girlfriend also vanishes and their mysterious cousin begins spying on them. The story takes place on Fear Street, where the siblings must investigate the disappearances while dealing with their increasingly suspicious cousin. This is the fourth book in the Fear Street series.