Sometime after the events of
the first film, Manny, Sid, and Diego live in a valley that is surrounded by a high ice wall on all sides and is inhabited by many other creatures. The trio discovers that the ice wall is actually a dam that is barely holding a
reservoir that could
flood the valley if it fails. A vulture tells them that there is a boat at the other end of the valley that may save them, but they must reach it in three days. A chunk of ice breaks off from the top of the dam, initiating their immediate evacuation. Manny is also struggling with the thought of possibly being the
last mammoth alive. Meanwhile, Cretaceous, a
Metriorhynchus, and Maelstrom, a
Globidens—both frozen since the
Mesozoic era—escape due to melting ice and seek to eat all the mammals they can during the flood. On their journey to the boat, the trio meet Ellie, a mammoth who believes she is an
opossum, and Crash and Eddie, two mischievous opossums whom Ellie believes to be her brothers. Sid invites them to join their journey to the boat, and Ellie accepts. After a dangerous encounter with Cretaceous and Maelstrom while crossing a pond, Ellie realizes that she is a mammoth. Manny begins to fall in love with her, but denies his feelings at first because he feels like he is replacing his deceased wife and child. Despite this bonding moment with Manny, she distances herself from him when he suggests "saving their species". Ellie and Manny later reconcile. The herd takes a break for the night. The next day, the group finds the boat behind a field of hot geysers. Manny, Sid, and Diego separate from Ellie, Crash, and Eddie when the two mammoths argue about which route is safest. Just as Manny, Sid, and Diego bypass the geysers, the ice dam fails, unleashing a flood upon the valley. Ellie, Crash, and Eddie, who took the safer yet longer way, are trapped inside a cave due to falling rocks. Crash and Eddie escape through a small hole and warn Manny, who rushes back to save Ellie. Cretaceous and Maelstorm ambush Manny underwater, but he tricks them into dislodging a boulder, thus freeing Ellie. Manny and Ellie reunite with the others atop a boulder, but the water is still rising. Meanwhile,
Scrat, after a series of misadventures to get back his acorn, climbs the adjacent glacial wall beside them and inadvertently creates a long crack when he punctures the ice. The crack widens into a gigantic
fissure which splits open the wall and drains the floodwaters, saving everyone; in the process, Scrat falls within the fissure and is washed away. A group of mammoths later appear from the fissure, proving to everyone that mammoths are not really extinct. Manny initially lets Ellie go with the mammoth herd, but after some encouragement from Sid and Diego to move on from his past, he catches up to her, expressing his desire to stay with her. Manny, Sid, Diego, Ellie, Crash, and Eddie then venture out of the valley. After falling into the fissure and nearly drowning, Scrat has a
near death experience, entering a
heaven full of acorns. Suddenly, he finds himself being "sucked back" just as he is about to reach a gigantic acorn. Scrat then discovers that he has been resuscitated by Sid. Scrat is enraged, believing that Sid stole his acorn, and proceeds to viciously attack him. ==Cast==