S.H.I.E.L.D. discovers the ancient city before HYDRA, but uncovering the secrets may require one of Coulson's team to make the ultimate sacrifice. Meanwhile, Melinda May and Skye race to get to Raina before Daniel Whitehall takes her.

Coulson and Whitehall's forces meet in an explosive confrontation that dramatically alters everyone's fates. Meanwhile, Skye discovers shocking secrets about her past.

Skye is torn between her loyalty to S.H.I.E.L.D. and her connection to the Inhumans as tensions rise between the groups -- and Coulson reveals a secret he's been hiding from even those closest to him.