The Challenge (Rystani #1)

She was shot protecting the president, and woke up naked, in the arms of a hunk...

A hunk named Kahn, who told Secret Service agent Tessa Camen an outlandish story about traveling through time, saving the world, and a Challenge only she can accept. Kahn offers her proof she can't refute: Tessa has been brought forward through time to save Earth by winning an intergalactic challenge.

Kahn only has a few weeks to train Tessa to use the psi-abilities he insists she has. He is confident in the success of a time-honored method that uses sexual frustration to bring out her powers, but Tessa is dubious. She's a martial arts expert and can fight her way through anything, but she's never had much luck with emotions.

Luckily for Earth, Kahn can be very convincing...