"The Beginning of the End" is the fourth season premiere, and 73rd episode overall, of the American Broadcasting Company's television drama series Lost.

Flashforwards show the post-island lives of Hugo "Hurley" Reyes (Jorge Garcia) and Jack Shephard (Matthew Fox).

[4] After being knifed in the back by John Locke (Terry O'Quinn) in the third-season finale, Naomi uses her satellite phone to call George Minkowski (Fisher Stevens) on the freighter.

Desmond Hume (Henry Ian Cusick) returns from the Looking Glass, bearing Charlie's final message that the freighter offshore is not owned by Penny Widmore (Sonya Walger).

Locke tells the castaways that they are in great danger and leaves for the Barracks with Hurley, James "Sawyer" Ford (Josh Holloway), Claire Littleton (Emilie de Ravin) and her baby Aaron, Danielle Rousseau (Mira Furlan) and her captive Ben Linus (Michael Emerson), Alex (Tania Raymonde) and her boyfriend Karl (Blake Bashoff), Vincent the dog (Pono)[8] and four other survivors.

Hurley willingly returns to the Santa Rosa Mental Health Institution, where he is visited by Matthew Abaddon (Lance Reddick), who claims to be an attorney for Oceanic Airlines.

[13] Jeremy Davies was cast as Daniel because he is one of the writer-producers' favorite character actors, and they think that his "transformative quality [and] the tremendous intelligence that seems to emanate from him ... seemed perfect for [the part]",[14] which was originally planned to be a recurring role.

[3] The ultimate title is a reference to a line in the previous episode when Ben warns Jack that contacting the freighter "is the beginning of the end".

Additionally, when Garcia was filming his interrogation scene in an aquarium, he was unaware that Charlie would be swimming outside and breaking the glass in the finished product.

[22] Charlie's swim was filmed weeks after the rest of the episode had been shot, alongside production of "Meet Kevin Johnson" and the Lost: Missing Pieces mobisodes in late November 2007.

[23] Most Lost episodes feature crossovers and "Easter eggs"—intentionally hidden clues and references to the show's mythology[24]—and "The Beginning of the End" is no exception.

[7] Robert Bianco of USA Today wrote that "returning with a heart-stopping, perfectly pitched episode ... Lost is an oasis in a strike-parched TV desert.

"[49] Mary McNamara of the Los Angeles Times described "The Beginning of the End" as an "emotion-churning chemical dump right in the old brain stem—horror, hysteria, regret, adrenaline and what ... will happen next?

[52] Diane Werts of Newsday raved the episode as "superb" and "insanely entertain[ing]" and concluded her review with "Lost seems to have found itself".

[53] Tim Goodman of the San Francisco Chronicle declared that it and "Confirmed Dead" "are roller coasters of fast action and revelation [that are] good to see".

[54] Matthew Gilbert of The Boston Globe pointed out that "Lost can still make the pulse race and the brain tingle ... [and] remains TV's most gripping serial".

[55] Alan Sepinwall of The Star-Ledger was unsure "if Lost is ever going to give satisfying answers to its many, many remaining mysteries ... but when it's as scary and hilarious and moving and exciting as these two episodes, I'm okay with that.

[58] Brian Lowry of Variety said that "Lost's return goes down like a welcome tonic as scripted TV fades to black ... providing an unusually generous array of juicy moments for the large (and, at times, neglected) cast.

[20] Frazier Moore of the Associated Press wrote that "Lost is further upping the ante, and heightening the pressure on us as the show's vast mythology continues to metastasize.