Karen's Spy Mystery — Ann M. Martin

From the bestselling author of the generation-defining series The Baby-sitters Club comes a series for a new generation!Karen the SpyNancy's family has hired somebody to take care of their house while they are on trip. Karen wants to make sure he is doing a good job. So she watches him closely. And she catches him snooping around! Karen is pretty sure he cannot be trusted. But she has to figure out what he is doing before she can turn him in.