|Father:||Thomas Walker (d. 2011)|
|Played by:||Jaden Harmon|
|First episode:||"The Good Soldier"|
|Last episode:||"Achilles Heel"|
Lucas first appears at his father's funeral with his mother and stepfather Matt saying, good-bye, unaware that he's been seeing his dad around.
Later, Lucas was later seen at the CIA Headquarters with his mother, being asked by David Estes, to identify his father as the man he saw near his school playground.