Season 1: Season 1 aired in the U.S. on Wednesday, September 22, 2004 at 8:00 p.m. and featured 24 episodes. When an Oceanic Flight 815 crashes on a deserted tropical island, the survivors must band together with strangers to survive. But their survival is threatened by a variety of mysterious things, including polar bears, wild boars, unknown giant creatures roaming the jungle, and the unsuspecting original inhabitants of the island, known as the Others. They also encounter Danielle Rousseau, a Frenchwoman on a scientific expedition that was stranded here 16 years earlier because of a shipwreck, and find a hatch that has been hidden above the ground. The survivors try to escape the island using a raft.
Season 2: Season 2*** has 24 episodes and airs on Wednesday, September 21, 2005 at 9:00 p.m. in the United States and Canada. The story continues the 44 days after the crash of Oceanic Flight 815 on a deserted island, focusing on the conflict between the survivors and the Others, as well as the conflict between science and faith. As mysteries are solved and new problems arise, new characters such as the survivors of the tail section of the plane and the other inhabitants of the island are introduced. The past of the survivors is also described in greater depth. As the hatch is explored, details of the Dharma Initiative (DHARMA) and The Hanso Foundation, the supporting organization behind it, are discovered. The mysterious "Others" go into action, and one of the survivors betrays the group and reveals the cause of the crash.
Season 3: ... Season 3*** consisted of 22 episodes (one of which was split into two parts) and aired on Wednesday, October 4, 2006 at 9:00 p.m. in the United States and Canada. The series returned on February 7, 2007 at 10:00 pm. The story continues 67 days after the plane crash with new survivors and island residents. On the mysterious island, the survivors learn about the Others and their history, and one of the Others joins the survivors and harms them. A war is about to break out between the Others and the survivors, and the survivors make contact with the Others to save themselves.
Season 4: Season 4*** consisted of 14 episodes and aired on January 31, 2008 in the United States and Canada. Due to the writers' strike, only 14 episodes remained in the season, with the first eight episodes filmed before the writers' strike, and the last six episodes completed after the writers' strike. After the eighth episode aired, a four-week run was cut short for the aforementioned reason, and the ninth episode didn't resume airing again until April 24th.
Season 5: Season 5*** had 17 episodes and aired on January 21, 2009. Season 5 follows two timelines: the first takes place on the island, with the survivors who did not leave the island experiencing irregular time shifts, culminating in them being trapped in 1977; the second continues the original timeline, depicting the survivors' story outside the island and their return to the island in 2007 aboard Ajira Airways Flight 316.
Season 6: Season 6*** had 18 episodes and aired on February 2, 2010. This season was also the final season of Lost. Season 6 also follows two timelines, both of which appear after the nuclear bomb explosion at the end of Season Five. The first timeline, known as "Flash Sideways World", is where Oceanic Flight 815 did not crash on the island. The second timeline, which is the original timeline, has the survivors time-shift back to the present after the nuclear explosion and have to deal with Jacob's death and face a mysterious man in black (Black Smoke).