The Citadel - Miles Michelle

Still lost in time, Skye and Dane face their most dangerous enemy yet.

As Skye Ransom and Dane Fortune time jump for the third time, they leave the frozen tundra of wintertime behind, hoping to land in their own century. That hope is crushed when they wake up in a jungle with oppressive humidity and a native tribe who mistakes Skye for the Goddess of Fire. Arriving at the tribe's village, they're introduced to Dr. Charles Ridgewood who gives them the impression he is not what he appears.

While waiting for the time bender to reset, they're honored guests of the Citadel's royal family. But when Dane falls ill, and Skye is captured, the true identity of Dr. Ridgewood is revealed and an old enemy returns to finish a job he started. 

Now separated, the two have to reunite before they're lost to each other forever.