Alex Caruso was a member of the Fifth Column. His father, Victor Caruso, fought in Vietnam while his grandfather fought in World War II. Alex wanted to make a difference like they did, so after hearing about the Fifth Column from Juan Solano, he decided to join the fight.
After the "John May Lives" message that interrupted Anna's broadcast ("Pound of Flesh"), Alex Caruso and his fellow Fifth Column members gained hope and became more active. They set up a meeting with other Fifth Columnists to obtain weapons. However, a Visitor (who later turned out to be a human named Jeffrey Barnes) showed up instead and killed everyone at the meeting except one: Alex Caruso.
The FBI investigated the attack and came across the bodies of Carl Bryant, Tom Maslon, and Juan Solano. The FBI found that they were Fifth Column planning a terrorist attack against the Visitors and that Alex had escaped the killer. Sarita Malik instructed Erica Evans to find Alex and to lead them to the Fifth Column.
After Jack Landry talked with Victor, he, Erica, and Kyle Hobbes found Alex hiding on the roof of a building. Instead of turning him in to the FBI, they needed Alex so they could get to the killer, who has a harddrive of names and addresses of other Fifth Column. They decided to use him as bait, so they sent a fake message over the Internet to meet at a fair after-hours in order to lure the killer. Alex had to stand in the center of the fair while Erica, Jack, and Hobbes hid and watched for the killer. They thought the killer was a Visitor, but he was actually a human (Barnes) in sniper position, indicated by his use of a gun instead of blades that V's usually use. Alex, unable to control his fear and panic, allowed himself to be exposed to Barnes, and he was shot in the back. He died quickly in Jack's arms as Jack recited a last prayer. ("We Can't Win")