Mike Slattery (Adam Baldwin) will have to lead the crew of the USS Nathan James in Captain Tom Chandler's (Eric Dane) absence in the upcoming season of "The Last Ship."

The last installment ended with a goodbye from the good captain. He resigned from his post in the Navy after the drama with Allison Shaw (Elisabeth Rohm) ended. They might have won the war, but Chandler lost a lot of people closest to him. His father was killed, as well as his friend, Tex (John Pyper-Ferguson). Although Chandler won't be on the ship in season 4, life moves on for the rest of the Nathan James' crew. Slattery will have to take over, especially when they face new challenges.

As per iTech Post, one of their missions will involve the help of Dr. Paul Vellek. Peter Weller will play the role of a specialist in genetic modification and plant biotechnology.

In a way, Vellek will be the second Dr. Rachel Scott (Rhona Mitra). She was the one who discovered the cure for the virus before her death. While it remains a mystery for how long Vellek will spend time with the squad, it is expected that he will play a huge role in saving what is left of humanity in the new season. Scott had been an integral part of the team before she was killed. Chandler and the others took her death badly.

Showrunner Steven Kane even revealed in a previous interview that one of the reasons why Chandler resigned was because he was still feeling guilty about what happened to her.

"How do you keep getting up, putting on your uniform and getting out there into the fight when everything you love and trust keeps getting taken away from you? ... That's a heavy burden. ... In some ways, Chandler is the Founding Father of this new country and no one begrudges him to a certain degree his desire to disappear for a while. But at the same time, there are still a lot of people who count on him as a Founding Father, so it's not going to be an easy transition," the executive producer said.

"The Last Ship" season 4 is expected to start airing in 2017.