Break of the Six (The Preston Six Book 4)

The Six return home from a charitable trip to help rebuild Vanar, and find their own world is in deep trouble. When a cough becomes much more than a common cold, an epidemic sweeps across the world. They have a suspicion of who is behind it all and rush to tell their missing member, unsure if she will even respond to their call.

Samantha Roslin has moved on. Putting her past--and the Six--behind her, she takes a position at a startup company in San Francisco. With eyes on her future, and also on her enigmatic boss, Zach Baker, she is ready to take the world by storm.

When Julie believes she's finally found signs of Marcus's technology on earth, it throws the group into a tailspin. They must find a way to stop Marcus before he has total control over Earth's people.