It’s fitting that the season four premiere of Lost, which aired last Thursday, should set a crucial scene at the cockpit of downed airliner Oceanic 815. Way back when the show first crashed onto ABC with J.J. Abrams’ brilliantly directed pilot episode, the cockpit buried deep in the jungle served as the destination for the first of several dangerous trips into the heart of the island. The invocation of the first episode signals a new beginning for the series, the blazing of new territory. And just as the third season’s finale brilliantly brought one chapter of Lost to a close, so do the first two episodes of season four jump-start another.

In Lost’s first three seasons, the island’s mysteries and the secret lives of the castaways, which were explored through flashbacks centered around a single character, evolved into a mythology as dense and elaborately conceived as anything on television—a virtual geek fantasia that incorporated everything from pirate ships and time travel to corporate conspiracies and whatever that four-toed statue thing is. Despite its complexity, the pulse of the show always lay in the survivors’ refreshingly straightforward objective: to survive and be rescued.

And there’s the rub at the heart of the show’s new story arc. Given that this is Lost, after all, and the series has three seasons to go, getting rescued is not going to be that simple. In tonight’s episode, the cavalry descends on the island in the form of four new characters: the meek physicist Daniel Faraday (Jeremy Davis), who reveals that rescuing the survivors of flight 815 “is not our primary objective,” short-tempered psychic Miles (Ken Leung), anthropologist Charlotte (Rebecca Mader), and helicopter pilot Frank Lapidus (Jeff Fahey). Meanwhile, back on the mainland, a quietly terrifying corporate rogue named Matthew Abaddon (Lance Reddick) seems to be pulling the strings.

At the end of season three, the writers, always one or two steps ahead of their voraciously speculative fans, dropped one of their most wicked twists ever: the flash-forward. Fragmented glimpses of the characters’ troubled future lives in civilization are juxtaposed with their on-island efforts to establish contact with the mysterious freighter offshore. It’s a tricky set-up, one that adds a thick new stratum to the show’s already densely structured narrative. At times, it’s hard not to hear the show creaking under the weight of its own bloated mythology, and the flash-forwards don’t quite have the emotional payoff that the flashbacks used to. The flashbacks provided each episode with a sense of unity and a deeper understanding of the show’s themes and characters. The flash-forwards, on the other hand, thrust us further and further into a new mystery in the making.

Season four draws the curtain on a darker, meaner Lost, a bleaker and less forgiving vision of survival and sacrifice, in which the rescuers may pose the greatest threat and the characters’ fates are sealed in glimpses of a grim future. If you’ve never set foot on the island before, now is the time to start.