SPOILER WARNING: This article contains major spoilers for "Absolution"/"Ascension," tonight's season finale of "Agents of S.H.I.E.L.D." As of publication, the episode had not yet aired on the west coast.
In "Absolution"/"Ascension," "Marvel's Agents of S.H.I.E.L.D.'s" two-hour third season finale, Lincoln Campbell (Luke Mitchell) met his untimely end as Daisy Johnson's vision of the future came to fruition, and weeks of show promotion and fan speculation paid off.
In the episode, Hive hijacked S.H.I.E.L.D.'s airbus with a handful of Inhumans and primitives; he planned to use the bus to launch a nuclear warhead filled with Holden Radcliffe's mutagenic formula into the atmosphere, so that it would transform any unsuspecting human who inhaled it into a mindless, subservient primitive. That way, he could connect with and control Earth's entire population.
After a mid-air confrontation between S.H.I.E.L.D. and Hive's forces on the bus, Coulson and his team discovered Hive's goal to steal the Quinjet, which has a much higher range than the bus. Yet since the warhead operated on a timer, there was no choice but to fly the Quinjet -- and the nuclear weapon -- into space, where it would disperse harmlessly. As the team argued over who would be the one to make this one way trip, Lincoln slipped into the Quinjet and jammed the controls before Daisy could -- but not before Hive attempted to stop them. Lincoln used his abilities to knock Daisy out of the Quinjet before she could protest, shut the door and took off, effectively trapping Hive and saving Daisy.
Daisy used a comm on the bus to contact Lincoln, and the two said their goodbyes and confessed their love for one another as he and Hive rocketed into space. Both Lincoln and Hive quietly came to terms with the situation, taking one last look at Earth as the timer ticked down. Once the Quinjet was safely above the Earth, the nuclear warhead detonated with the two on board. Thanks to Lincoln's sacrifice, countless civilians were saved and Hive's plan -- as well as his control -- were foiled.
After the explosion, the episode jumped six months into the future, where Coulson and Mack are in the middle of a stakeout. As it turns out, they're pursuing Daisy, who has gone rogue. They catch her in the act of helping Charles Hinton's wife and daughter, but she manages to escape them by using her abilities.
The scene then cuts to Holden Radcliffe, who has just been cleared in court for his actions in Hive's plot. As he enters his office, he has a conversation with an AI he calls AIDA. He tells her that it's time to celebrate, just before he reveals his work with Fitz on L.M.D. -- that is, Life Model Decoy -- technology. The shot cuts to an obscure figure behind frosted glass and he tells AIDA that it's her birthday, hinting that he will soon upload her into this new body.
"Agents of S.H.I.E.L.D." will return for its fourth season on ABC this fall.