Daryl, Carol, Aaron, Jerry, Connie, Kelly, and Magna are trapped on a ledge in the cave above the walker horde and spot Alpha watching them from above. Leaving, Alpha orders two Whisperers to ensure that the group doesn't escape.
Unable to climb back up, the group spots water across the cave that Daryl realizes is coming in from the outside. The group makes a perilous series of jumps across stones between the two sides of the cave, making it safely despite a few mishaps. Searching the other side, Daryl is able to find a way out using a lit match to find a breeze as the other realize that the walkers must be Alpha's horde and there are likely Whisperers inside the cave with them.
Eventually, the group stops and while a restless Magna searches for where to go next, they come under attack by Whisperers. The group kills most of the enemy while the rest flees and Jerry notices an arrow pointing to where to go next. Following the path, the group discovers that it leads into a narrow passageway which causes problems for the claustrophobic Carol. As the group crawls through a low part of the tunnel to an opening to a larger part of the cave, Jerry gets stuck due to his height and attacked by following walkers which bite at his foot. The others pull Jerry free and discover that his boot protected him from getting bitten.
Across the way of the new part of the cavern, Magna spots a hole in the celling with light pouring in from the outside, but discover that they are also over a steep drop leading to the horde below. Making their way through a boarded up opening, the group discovers an old mine station, and a blockade where a hole in the celling has opened from a collapse and a box of old dynamite that Jerry rejects using as it is too dangerous. As the group works to widen the hole, Carol takes a stick of dynamite and sets it up on a ledge, knowing that collapsing the cave there can take out half of the horde. After she nearly falls, Carol is saved by Daryl who talks her out of her plan. However, the dynamite is accidentally knocked into the pit in the process and explodes, causing the mining tunnel to begin to collapse.
Jerry holds up the celling using a support beam while the others climb out of the hole. Upon emerging, Kelly finds more Whisperers and kills them with the help of Aaron after he emerges. Magna and Connie go back to help Daryl and Carol, but have to fight off more Whisperers. Unable to hold up the celling anymore, Jerry flees through the hole and the remaining dynamite detonates, collapsing the tunnel and trapping Magna and Connie.
Though Daryl tries to dig back into the cave, Aaron warns that it will take them at least a week and Kelly points out that the explosion will draw in walkers and Whisperers from all around. Angrily ignoring Carol, Daryl orders the others to return home and let everyone know that they have found the horde. As the Whisperers got out before them, Daryl knows that there must be another way in and sets off in search of it.
Daryl arrives at the entrance to the cave in time to witness Alpha leading the horde out though with no sign of Magna or Connie.
At the same time, Mary visits Alexandria and offers information about the cave in exchange for being allowed to see her nephew. Mary shows Gabriel, Rosita, Laura and Scott the cave's location on a map and warns that while there are other entrances, she is not sure where and they will all be guarded. However, before they can lead a rescue mission, a call from Echo Post about a supposed herd draws out most of Alexandria's forces.
When Aaron returns to Alexandria in the aftermath of Beta's attack, he reports on the events in the cave and how most everybody made it out.
During the attack on the Hilltop, Magna appears, using walker guts to blend in with the herd. Magna reveals that she and Connie disguised themselves with walker guts to get out, but eventually got separated in the horde. As a result, Magna doesn't know if Connie survived or not.