Donald Lydecker is played by John Savage, who has also appeared in a couple of episodes of Star Trek: Voyager and an episode of Law and Order: Special Victims Unit.

Lydecker is one of the main people working at Manticore. After the death of his girlfriend, he seemed to have just thrown himself into his work. He actually used a bit of his dead girlfriend's DNA in Max's.

After the escape of twelve of the X-5s, Lydecker pretty much devoted his whole life to tracking them down. He got Brin back after a mix-up in her genes that basically caused her to start aging rapidly. If she hadn't gone back, she would have died.

Lydecker helps Max, Logan, Zack, and others in their attempt to destroy Manticore. In a way, he actually does seem to care about the X-5s, almost as if he sees them as his children. Not a whole lot more is known about him, though, as he probably dies during the second season.