NCIS is finally back and so is Mark Harmon as "Gibbs." Season 19 kicked off on Monday, picking up from last season's cliffhanger of "Gibbs" escaping an explosion on his boat.

This season also carries extra drama, given all the rumours about Mark Harmon possibly leaving and new cast members joining the show. So here's what actually happened in the season premiere.

NCIS season 19 premiere: Recap of "Gibbs" in episode 1

At the end of last season, "Gibbs" had teamed up with journalist "Marcie" to investigate a serial killer. But the case got dangerous when "Gibbs" was nearly killed by a bomb on his boat.

Now for the new episode. "Gibbs" did survive the explosion, but it wasn't a clean escape. He was impaled with a piece of shrapnel and ends up floating away in the lake, wounded. Meanwhile "Torres" and "McGee" investigate the incident.

"Gibbs" eventually wakes up in a mysterious barn. Though still injured, he discovers he's been treated by a couple who discovered him by the lake.

The man and woman believe "Gibbs" is mixed up in gang violence, but he convinces them he's an agent when he identifies a phoney cop snooping around. So they let him take a gun and motorbike to a nearby ranger station.

In the meantime, the serial killer has struck again: a woman's body is recovered near the same lake, leading "McGee" and "Torres" — with newcomer "Jessica Knight" — to the same place as "Gibbs."

They all end up at the station, but "Gibbs" doesn't receive the team too warmly. And they end up facing down a gang because the abandoned station turns out to be a drug house.

In the end, the reunited NCIS team takes down the drug dealers, along with that fake cop, but the mystery of the explosion and the active serial killer remains.

"Gibbs," of course, has been away from NCIS, but the episode concludes with him seemingly agreeing to work with "McGee" on the serial killer investigation.

It's unclear if "Gibbs" will return to his team, however. But it was a good start to season 19, after it was reported that Mark Harmon, the popular and longtime star, could appear in only "a few" episodes this season.

NCIS season 19 gets right back at it on Monday next week with Episode 2.