Coulson and the Agents of S.H.I.E.L.D. are thrust backward in time and stranded in 1931 New York City. With the all-new Zephyr set to time-jump at any moment, the team must hurry to find out exactly what happened. If they fail, it would mean disaster for the past, present and future of the world.

With the identity of the timeline-unraveling "thread" revealed, the team's mission to protect him at all costs leads each agent to question their own values. Is preserving the future of the world as they know it worth the destruction they could prevent?