From Time to Time: the First Book: Varta's Act

Lars Nathan is an ordinary man doing an ordinary job. He wakes in the morning and goes to work like any other normal person. However, one of Nathan's colleagues has gone rogue. Nathan is given the task by his superiors to hunt down and bring back his co-worker who also happens to be a friend. This will be Agent Lars Nathan's most difficult assignment yet and will determine his future with the Agency. You see, Nathan works for the TTA. A government agency dedicated to stopping people from escaping to the past. Nathan is the best they have and he must use everything at his disposal to bring his friend back to face his destiny.