Ava Frost has a new mission and a new enemy. To stop the impending alien invasion of Earth, she and her brother Elias must use their special connection to computerized consciousness Ian 2 to infiltrate Space 51, an illegal base in orbit around Saturn's moon.

The human alien hybrids on Space 51 could play a vital role in defeating a hostile alien race that nearly wiped them all out once…and plans to try again. But can they be trusted? As Ava struggles to figure out if working with the human aliens of Space 51 is enough to stave off the coming invasion, she becomes the target of a malevolent telepath who may be eavesdropping on her every conversation.

Needing to escape the telepath and severe the connection, Ava returns to Earth with Elias and discovers information about a secret sect of humans called MJ-21, which was initially formed on Earth but eventually abandoned it due to political dissention. Their mission is to maintain a presence among the human alien races throughout the galaxy, no matter how many lives it costs. Can Ava and Elias convince MJ-21 to join the fight against the coming invaders and save the billions of people they left behind? Or will past agendas and political ambitions once more leave Earth an easy target?