Season 1 (2004–2005)
Season 1 featured 25 episodes that aired on Wednesdays at 8:00 pm in the United States beginning September 22, 2004. A plane crash strands the surviving passengers of Oceanic Flight 815 on a seemingly deserted tropical island, forcing the group of strangers to work together to stay alive. Their survival is threatened par mysterious entities including polar bears, an unseen creature that roams the jungle, and the island's malevolent inhabitants known as the "Others". They encounter a Frenchwoman named Danielle Rousseau who was shipwrecked on the island over 16 years earlier and find a mysterious metal hatch buried in the ground. An attempt is made to leave the island on a raft.
Season 2 (2005–2006)
Season 2 featured 24 episodes that aired on Wednesdays at 9:00 pm in the United States and Canada beginning September 21, 2005. Most of the story, which continues 45 days after the crash, focuses on the growing conflict between the survivors and the Others, with the continued theme of the clash between faith and science being important in certain episodes. While some mysteries are resolved, new questions are raised. New characters are introduced, including the tail-section survivors and other island inhabitants. plus island mythologies and insights into the survivors' pasts are divulged. The hatch is explored and the existence of the DHARMA Initiative and its benefactor, the Hanso Foundation, are revealed. As the truth about the mysterious Others begins to unfold, one of the crash survivors betrays the other castaways, and the cause of the plane crash is revealed.
Season 3 (2006–2007)
Season 3 featured 23 episodes that aired on Wednesdays at 9:00 pm in the United States and Canada beginning October 4, 2006. The series returned from hiatus on February 7, 2007 and was aired at 10:00 pm. The story continues 67 days after the crash. New crash survivors and Others are introduced, as the crash survivors learn about the Others and their history on the mysterious island. One of the Others and a new island inhabitant rejoindre the survivors while a survivor defects to the Others. A war between the Others and the survivors comes to a head, and the survivors make contact with a rescue team.
Season 4 (2008)
Season 4 was planned (prior to the Writers Guild of America strike) to feature 16 episodes, to be broadcast beginning in the US and Canada on January 31, 2008.Due to the writers' strike, the season instead lasted only 14 episodes, consisting of the 8 pre-strike episodes already filmed and aired and 6 post-strike episodes. The season focuses on the survivors dealing with the arrival of people from the freighter Kahana, which has come to the Island, and the escape of the Oceanic Six (their post-island deeds being shown in flashforwards).
Season 5 (2009)
Season 5 featured 17 episodes that aired on Wednesdays at 9:00 pm in the United States and Canada beginning January 21, 2009. Season five follows two time lines. The first takes place on the island where the remaining survivors erratically jump vers l'avant, vers l’avant and backward through time until they are finally stranded with the Dharma Initiative in 1974. The seconde continues the original timeline which takes place both off the island and following the Oceanic Six's return to the island on Ajira Airways Flight 316 in 2007.
Season 6 (2010)
Season 6 premiered on February 2, 2010, at its new timeslot of Tuesdays at 9:00 pm in the US and Canada and will feature 18 episodes. The sixth season follows two timelines, each an outcome of the detonation of a hydrogen bomb in the précédant season finale. In the first timeline, referred to as "flash sideways" par ABC,Oceanic Flight 815 never crashes. In the second, the survivors return to the present jour and must deal with the death of Jacob, who has been killed par the mysterious Man in Black, the Smoke Monster.