There's a flashback of Gavin and Eve by the wisdom tree. It's covered with notes and photos, including their first anniversary. She hands him an ultrasound photo off the tree, and he's so excited. He wants to learn about all future pregnancies that way as they embrace.

Then, we see Gavin and the group at a gas station in 1965. They're headed to one of Rysander's base operations to destroy the chip and find Eve. Sam returns with a lead. He thinks Riley is at Ceders Hospital. Helena says they have limited time and gives him the car, saying they'll find another.

In 10,000 BC, Ty informs the others that the blue aurora could return them home to 2021. Ruth offers to gather the others, but Scott refuses to go until they locate Petra. Scott, Lucas, and Ty interrogate the guards about Petra and find Paara's purse in the jeep, which makes Ty panic.

The guard admits they found some dead villagers about five miles east. The men comfort Ty and head that way to search.

Gavin knocks out a guard at the Pasadena Research facility but finds Eve's cell empty. Helena finds an order to relocate a prisoner to the base in 10,000 BC and thinks Maya is on to them.

Sam finds Riley at the hospital, but she's not in good shape. She has a torn diaphragm, and Sam wants to get her to a modern hospital, but she's having difficulty breathing.

In 10,000 BC, Scott, Lucas, and Veronica help Ty look for Paara. Scott tries to get Ty to talk, and Ty admits Paara changed his life. Ty also admits the 2021 version of Scott told him about his broken engagement, and he encourages Scott to fight for her.

In 1965, Sam is dressed as a surgeon and doing an experimental lap, which won't be done for another decade. He promises to be a better father, but she needs to pull through.

Back in 10,000 BC, while Gavin distracted the guards, Izzy crashed into a military vehicle. Both were shocked to see Josh in the back of the car. He had been in a cell with Eve before being transferred here.

They're confused about where Eve is, wondering if Helena found her when Sam arrives. Sam shares an emotional goodbye with Gavin when he explains he's taking Riley to 2021 for medical attention.

Lucas and Veronica have a long talk about how he's ready to return to 2021. She and Scott made a significant impact on his life. Veronica starts having cramps, and he reassures her the baby will make it.

Scott and Ty find Paara, and a beam is stuck on her. She knew Ty would come, and he reassured her this was home. Scott returns with another log for leverage to ease it off of her.

Another dinosaur arrives as soon as they do, so they run to Lucas's jeep.

1965 Helena arrives and says she and Eve fought them off, but more arrived. It seemed skeptical, but Eve wanted them to stop the war against Maya, so everyone returned to 10,000 BC again.

The entire group stands united as they send Veronica through the 2021 aurora. Gavin thanked Lucas for staying to help. They see a T-rex and decide to use it to their advantage.

The Harris family, Scott, and Lucas head toward the base in the jeep, with the dinosaur following them. They lead it right to it, so Maya and her guards are distracted. They make their move as soon as it breaks down the gate and attacks the base.

Scott sees Petra being interrogated by the guards, so he and Lucas race off to rescue her. The Harrises find the chip as the men and Petra return.

Maya stops them from leaving and demands the chip, but Ty and the fort tribe arrive with bows and arrows and shoot Maya. Chaos ensues as Scott and Lucas fight military soldiers.

One guard with a knife tries to attack Izzy, but Leyla saves her. Gavin interrupted their moment. The aurora disappears, so they need a new plan.

Just as the entire group is about to leave on Gavin's time machine, Maya arrives and pulls a gun on Josh. She demands the chip for his life. Gavin almost falters, but Josh screams not to. Gavin throws it in the air, and Helena shoots Maya.

What an exciting moment as the plane takes off. When they land, Gavin promises to keep in touch with Helena. They stop at the hospital so Josh and Riley can reunite.

Veronica and Lucas are checking her sonogram as Scott interrupts the moment. They're like family now. After that, he finds his old fiance, proves that he's changed, and asks for another chance.

Sam reunites with the rest of his family, and runs into Gavin at the hospital. Gavin remembers where Eve could be.

Gavin leads the kids to the wisdom tree, and after hours, Eve finally arrives and embraces Josh first, and then Izzy and Gavin. The reunited family walks off into the sunset.