|Portrayed by||Zeljko Ivanek|
|First appearance||Dead Man Walking|
|Also known as||Dr. Horn|
|Residence||Guantanamo Bay Cuba (Formerly)|
Gulf of Mexico (Temporary)
|Affiliation||Department of Defense(Formerly)|
|Family members||Marcus Horn|
Unnamed Mother (Deceased)
Dr.Calvin Horn was a member of The Patriots. In a conversation with Rachel, he described himself as the President's Chief Science Adviser.
When Horn was a boy he watched helplessly as his mother died of an unnamed illness. His father was deeply religious and tried to pray the illness away, but to no avail. Horn did not believe in miracles and offered several times to get medicine from his friend's father, but his father refused every time. One day Horn secretly got the medicine and gave it to his mother. However his mother died and his father blamed him for her death because he gave her the medicine. When Horn grew up he became a scientist working for the D.O.D., helping with their alternative energies project. While working there he meet Rachel Matheson and worked with Ben Matheson's team on the project.
After The Blackout he was on the first boat leaving D.C. with President Jack Davis and Randall Flynn heading for Cuba. Some time later he moved to a base in the Gulf of Mexico. Here he examined the burned bodies sent by Truman. When he learned the bodies came from Willoughby and that Rachel was in Willoughby he ordered everything packed up, saying that they were heading to Willoughby.
A couple of days later he arrived in Willoughby, Texas and met with Rachel to discuss the Nantes. He knew they must have been reprogrammed and he figured that it was Rachel that reprogrammed them. When he found out it was not her, he met with Dr. Porter asking him to tell him about Aaron. Gene planned to hand over Aaron to Horn, but Miles saw through their plan and snuck Aaron and Cynthia out of town. Once he found out that Aaron escaped he ordered Truman to send all The Patriots out and find Aaron; he also warned Gene to find Aaron before he found Rachel or else he would kill her.
The Patriots eventually found Aaron and Cynthia and brought them back to their secret headquarters. He told Aaron he was not going to hurt him, he just wanted to help him better understand the Nanotech. He proceeded to experiment on Aaron by cutting him and see how he miraculously healed every time. He told Aaron that he wanted to see if Aaron could heal someone else. He had his men bring in Cynthia and stab her in the side. By doing so he caused Aaron to knock everyone out and escape.
Upon awaking he noticed Aaron had escaped, he ordered him tracked down and found. He followed Aaron's trail through The Patriots' secret tunnel and into the woods outside of Willoughby. He ordered his men to fan out and search, but his search was impeded by Miles, Rachel, Charlie, and Monroe. With the fog thickening, Martin Shaw told him he needed to fall back. With his condition worsening with his tumor he ignored Shaw and continued the search. He soon received word that Aaron was at the abandoned High School, and ordered the Patriots head in that direction.
When they arrived they were met with resistance from the four who were helping Aaron and Cynthia escape. Monroe, Charlie, Rachel, and Miles held them off long enough, but they were all eventually cornered. While Rachel tried to protect an unconscious Miles in the library, Monroe and Charlie were busy fighting them off in the gym, and Aaron and Cynthia were confronted by Horn himself. He ordered Aaron to remove the tumor from his brain, but when he didn't he killed Cynthia and prepared to kill Arron. Aaron called to the Nanites, who appeared and asked for his orders. He told them to kill Horn and all the Patriots attacking saving Miles, Rachel, Charlie, and Monroe in the process.
Later, when Aaron was trapped in a dreamworld by the nanites, Dr. Horn was used as a portrait for Aarons nightmare.