Invasion is an American science fiction television series that aired on ABC for only one season beginning in September 21, 2005. Somewhat similar to Invasion of the Body Snatchers, the show told the story of the aftermath of a hurricane in which water-based creatures infiltrate a small Florida town and begin to take over the bodies of the town's inhabitants through a cloning process (first by merging with and then unknowingly replacing them). The show was produced by Shaun Cassidy Productions and Warner Bros. Television.
Due to Hurricane Katrina in 2005 and the aftermath in the southern United States, early on-air promotions were quickly pulled by ABC. The advertising then switched emphasis completely to the alien invasion aspect of the series, while the hurricane received no mention. The premiere was also preceded with a warning that the show featured images of a fictional hurricane that viewers could be sensitive to.
Invasion received mostly positive critical reception. Metacritic gave the season a score of 72, making it generally favorable. The show was nominated on the 32nd Saturn Awards for Best Network TV Series and Best Television Actor for William Fichtner. It has been included in many "gone too soon" lists. In the independent web critic, Critics at large, the show was reviewed as a Lost Treasure. On a chat live between Bullz-eye.com and Tyler Labine, the actor says: "Invasion did get lots of love. Critics loved it. There was quite a huge following by the time we got cancelled. It was just the network didn’t love it, that’s all." He also acclaimed Shaun Cassidy's writing, calling him a "mad genius".
According to Nielsen ratings, the series premiere garnered 17 million viewers airing after Lost. By the November 30, 2005 episode, the show was only garnering 10 million viewers.
For the episodes shown on January 11, 18, and 25 the Nielsen Ratings only reached 9.7 million, 9 million and 9.3 million, respectively. It had lost nearly half of the first episode's audience, far behind CBS's CSI: NY, which had 13.7 million, 15.5 million and 14.9 million, for the same period. The show was then put on hiatus for the second time, during which time it was replaced with The Evidence.
In the "August 14–20, 2006" issue of TV Guide, actor Tyler Labine (who played the character Dave Groves) relayed what creator Shaun Cassidy had planned for the following season, saying that Cassidy had said, "Larkin was going to be presumed dead. Russell and I were going to join forces against Tom. Tom was going to find out that his first wife was alive and running this whole military operation, and she was Szura's boss."
William Fichtner (who played the character Tom Underlay) also stated the following about the development of the storyline:
"There was something in there that I thought that was so good," said Fichtner. "I discovered who it really was who was orchestrating [everything]. I didn't even see it coming from a million miles away. It was my [first wife, Grace], who got on the plane with me. Two people lived after that  plane crash, not just one. She went in another direction altogether. It's amazing. It was, 'ah, what you could have done with that.' "
Season 1 Episodes [Complete Series]
1.02 Lights Out
1.04 Alpha Male
1.05 Unnatural Selection
1.06 The Hunt
1.07 Fish Story
1.08 The Cradle
1.09 The Dredge
1.10 Origin of Species
1.11 Us or Them
1.14 All God's Creatures
1.15 The Nest
1.16 The Fittest
1.17 The Key
1.19 The Son Also Rises
1.20 Run and Gun
1.21 Round Up
1.22 The Last Wave Goodbye