| Plot |
| 1x01 - Trees Made of Glass (1): | | A mysterious alien object attacks a Naval ship and crew. Dr. Molly Anne Caffrey, a government contingency analyst, is contacted by the Deputy National Security Advisor, J.T. Baylock, to investigate the incident along with a special scientific team of her choice. |
| 1x02 - Trees Made of Glass (2): | | Gunneson reappears in Caffrey's house. Meanwhile, Lucas, Nigel and Ramsey try to break down how the alien signals and DNA operate and come up with some interesting theories. Cavennaugh's team tries to locate Gunneson other shipmates. |
| 1x03 - Blood of the Children: | | When a man at a fast-food restaurant is found with his head imploded, Molly and her Red Team investigate and begin to suspect the involvement of a group of military cadets. |
| 1x04 - The Burning: | | A patient at an psychiatric hospital in Ohio escapes and Molly believes he may have been infected by the alien signal after paintings of glass trees are found in his cell. After further investigation, it is suspected one of the missing Big Horn crew might be involved. |
| 1x05 - Shock: | | After a shipyard gang bust, a suspected fugitive Big Horn crewmember kills a police detective. Molly and Cavennaugh go undercover as Homeland Security agents. Unbeknownst to them, the real Homeland Security department is on the case. |
| 1x06 - Pulse: | | As the signal from the Big Horn invades a Miami rave, the team investigates who have been infected, trying to prevent the signal from spreading to the population. |
| 1x07 - The Order: | | Molly and Cavennaugh investigate a newspaper leak regarding the Threshold program which might turn out to be an inside job. The Red Team look into a case of residents of a small town dreaming of trees made of glass. |
| 1x08 - Revelations: | | Molly and Cavennaugh discover some strange happenings in a missing Big Horn crew member's hometown when they investigate the disappearance of a Threshold field agent. |
| 1x09 - Progeny: | | Three women from completely different walks of life show signs of being infected, leaving Molly and the team to try to find the common thread and stop the spread of contamination. |
| 1x10 - The Crossing: | | Molly and Baylock realize the Threshold detainees must be moved immediately to a more secure facility in West Virginia when a prisoner attacks and infects a security guard, then tries to break himself and other infected prisoners out of their cells. |
| 1x11 - Outbreak (a.k.a. Escalation): | | As the threat from genetically modified food grows, the Red Team recruits a feisty botany expert. And Molly learns the aliens' shocking motive. |
| 1x12 - Vigilante: | | A doctor launches a crusade to murder infectees, but he puts ordinary people at great risk. Ramsey's decadent lifestyle puts him in close contact with the infection. |
| 1x13 - Alienville: | | The taut drama series reaches its powerful finale. Can Molly and the Red Team prevent an alien infection pandemic?
Molly Caffrey and Cavennaugh go out to a town call Allenville in search of a Doctor who they think is infected and find more then they were looking for.
Meanwhile things at threshold get heated with the pregnancy of the infected woman coming to an end. |
| 1x14 - Head Trip: | | Molly gains super strength like the infectees as she starts to show signs of turning and gets in a fight with a security guard throwing him across the room.
Molly also meets a new guy, and a romance begins between them. |
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