The Observer Effect

Time calls the shots.
Unwitting time traveler Joseph Bridgeman is adjusting to life in the present and wondering if his traveling days are behind him. But when he's contacted by the Continuum, an organized group of time travelers based in the future, he learns his career is just getting started.
The Continuum needs Joe's help. One of their operatives is missing, last seen in nineteenth-century Paris, and they believe Joe's ability to see the past might be the only way to find him. Teamed up with Gabrielle Green, an acerbic, wisecracking traveler, Joe heads back to 1873 on his most dangerous mission yet, one that will take him deep inside a burning opera house.
But how will Joe succeed when his new companion clearly hates his guts, the missing traveler disappears the second anyone sets eyes on him, and a familiar foe threatens to trap them in the past for good? With help on hand from his best friend, Vinny, and mysterious clues hidden in his sister Amy's paintings, Joe must hone his gift, develop new skills, and figure out a way to complete his mission before the blazing inferno comes crashing down around them all.