After reluctantly returning to her tourist-trap hometown of Roswell, New Mexico, the daughter of undocumented immigrants discovers a shocking truth about her teenage crush who is now a police officer—he’s an alien who has kept his unearthly abilities hidden his entire life. She protects his secret as the two reconnect and begin to investigate his origins, but when a violent attack and long-standing government cover-up point to a greater alien presence on Earth, the politics of fear and hatred threaten to expose him and destroy their deepening romance.

Based on the Pretty Little Liars series of young adult novels by Sara Shepard, the series follows the lives of four girls — Spencer, Hanna, Aria, and Emily — whose clique falls apart after the disappearance of their queen bee, Alison. One year later, they begin receiving messages from someone using the name "A" who threatens to expose their secrets — including long-hidden ones they thought only Alison knew.