Travelers are people who somehow have the ability to travel through time. When this happens, they are "assigned" to certain people, and must follow them and change certain events of their lives.
- Dan Vasser- recently discovered he could travel, Dan has only told his wife, Katie, though his son has seen him travel, and knows that Dan isn't normal.
- Livia Beale- revealed to have been traveling even before she met Dan, implying that she has been making trips through time for a matter of years, one of which saved her life from a terrible plane crash.
- Evan Patterson - In the "final" episode, "Perfidia", we discover another traveler, Evan, who, sometime in the past, made some changes to the timeline that he now regrets. We soon discover than Dan began traveling just moments after Evan died.
- Other individuals who have hinted at having some knowledge of the travelers include:
- Elliot Langley speaks about time travel in the context of a supposed novel that Dan is writing, but the subtext of their conversations, and a strange call with Langley in the past, suggests that he knows more about the travelers.
- After a weeks-long investigation of Dan, FBI Agent Richard Garrity, who was working without an official case file from the FBI, reveals in "Blowback" that he has observed evidence of Dan in more than one time zone. He cryptically thinks out loud to Jack and notes that "they" always have a problem with getting currency, suggesting that he's familiar with the travelers.
Whenever Dan is about to travel, he gets a headache, giving him warning and allowing him to go to a private location so as not to be seen vanishing, which happens with a blue flash of light and a ripple in the air. When arriving in a different period of time, Dan almost immediately encounters someone, and interferes in a major event in their lives. After changing history, Dan is sent back to his time, sometimes returning mere minutes after his departure, sometimes returning hours after it. It is not known if Livia goes through the same ordeal when traveling, if she has any control over it, or if she even returns to the present at all, as she's presumed dead there. However, when she has been seen traveling on occasion, her process is almost the same as Dan's, except that she disapears with a yellow flash of light, as opposed to Dan's blue.
Dan has no control over his traveling, which directly interferes with his life, such as when he vanishes during a fair, leaving his son lost and unattended on the street. He also cannot change history other then the events of people he has been "assigned" too. This is seen when Dan is unable to save Charlotte Skillen during the Loma Prieta earthquake (although, this was due to Livia's interference). While Dan was able to save a little girl from Aeden Bennett, even though his focus was supposed to be on Emily, this did not turn out so well for him, as Bennett was able to find him in his own time, after being released from prison.
- After returning home from one of his "trips," Dan begins raiding his fridge, and tells Katie that he's always hungry when he returns and doesn't know why.