A Sword in Time: Thief in Time, Book 3 (Unabridged‪)‬

Modern girl DaVinci doesn't recognize her life after a quick trip to the past turns her world upside down. Meanwhile Quintus, a swoony soldier stuck in this century from 53 BC, is set on time traveling to make good on a promise to Julius Caesar. When Quintus and DaVinci accidentally travel together to ancient Rome, the feisty pair are in danger of falling in love, if they don't kill each other first. One thing is clear: They've got to learn to get along if they want to make it back to the 21st century alive. 

The Thief in Time series features exciting young adult romances packed with historical detail and plenty of action.