Riggs is found naked, sleeping on the beach. The cops think he's dead, but when they poke him he wakes up, gets up, and walks home.
Murtaugh is prepping ribs for dinner later. Trish asks about the previous case, and Murtaugh tells her more than he wanted.
Riggs is heading out to Murtaugh's place when he gets a call from his realtor in Texas telling him a young couple wants to by his house. He has flashbacks and tells the realtor to sell it. Instead of going to Murtaugh's house, he goes to a bar where he purposely flirts with a biker's girlfriend and gets beat up in the process.
The Murtaugh family is patiently waiting for Riggs who hasn't shown up. Murtaugh calls Riggs who is lying on the ground all bloody. Murtaugh is not happy, but Riggs says nothing about the fight.
The next day they are waiting outside the captain's office and Murtaugh is going on about Riggs blowing them off the night before. They're called into the office where Avery tells them how much money they've cost the city with their antics.He sends them out on a noise complaint call.
When Riggs leaves, Murtaugh asks Avery about Riggs being allowed on the field, and Avery tells him he doesn't get why Riggs is still out there, that he must have friends in powerful places.
At a house party, a guy brings in a stash of guns for a buyer to look at. He notices something outside and takes a picture. He's told to take care of it.
Riggs and Murtaugh show up at the lady's house who made the complaint. She says the neighbors have been partying all day and she smells pot. Riggs and Murtaugh say they smell freshly baked coffee cake and are about to go in for a slice when they hear gunshots. The gun guy has taken one of the guns he brought and fired on the crowd outside.
Riggs and Murtaugh head over to the house where the shots came from and chase after the gun runner who hops in a propane truck. Riggs steals a motorcycle while Murtaugh takes the car. Riggs exchanges gunfire with the guy, but crashes the bike. Murtaugh blocks the guy's path, but doesn't take the shot. Eventually the tank blows up because Riggs' bike got caught underneath the truck creating sparks.
Scorsese is at the party house giving details. Riggs doesn't think the boxer was the target. After looking at some photos on the phone they think a waitress at the party might've been the real target.
Back at the department, they are explaining the case to Avery who interrupts them to introduce them to Bennet Hirsch, an ATF agent now involved in the case because of the military style of the gun. Avery puts them on the case.
As they're leaving, Murtaugh runs into Dr. Cahill and tries to get some information about Riggs, but Cahill doesn't share.She's sitting at Riggs' desk when he shows up looking for his flask. He goes into the bathroom and she follows. She's still looking for information from him and tells him he needs to talk if he wants to continue to work and carry a gun.
In the medical examiner's office, Scorsese tells Murtaugh that the waitress was pregnant. Bailey comes in and tells him she found the address of the girl. Murtaugh and Riggs arrive at the address, but no one is home so they break in after hearing a cat screech which they determine is a girl's scream. The girl eventually shows up and they chase her down. Riggs ends up on the roof with her, while Murtaugh is down on the street. A sharpshooter is on another roof ready to take them out when Riggs gets a warning shot from Murtaugh alerting him to the situation. He takes Natasha and leaps off the building into an apartment in the building across the way.
Riggs is questioning Natasha while Avery, Cahill, and Murtaugh wait outside. Avery is concerned about Riggs being on the job and Cahill tells them he lost his wife and child less than a year ago.
Riggs promises Natasha he's going to keep her and her unborn child safe. They put her in protective custody. As Riggs is leaving, Murtaugh brings up the blown off dinner the other night and invites him over.
Riggs is having dinner at Murtaugh's house. Trish and Murtaugh go upstairs to take care of the baby when Roger tells Trish about Riggs' baby. Trish is concerned that Riggs' is not the right partner for Murtaugh.
Murtaugh goes back downstairs and finds everything cleaned up. He finds Riggs passed out outside.
Riggs and Murtaugh show up at a meeting at the office the next day with Avery, Scorses, and Hirsch. They learn the weapons are housed in a military facility in Sand Diego. They head out there whie Hirsch finds out where Natasha is holed up.
They get the information they need in San Diego and learn that it is Hirsch who is behind the sales. They head back and Murtaugh tries to get someone to the safehouse, but Natasha is gone, Hirsch having got her.
Somehow Riggs and Murtaugh find out where they took Natasha and raid the warehouse. A shootout ensues which ends up with fireworks blowing up allowing Riggs and Murtaugh to escape with Natasha.
Back at the office, Avery sees the fireworks and wonders where Riggs and Murtaugh are.
Riggs is back in Cahill's office still refusing to talk about anything serious. Murtaugh is in the main office telling his story when Trish shows up. She's mad he took his watch off and tells him he can't have ribs if he doesn't wear the watch.
Riggs is in the elevator when Trish comes in. She wants to know if he's crazy. When he says yes, she tells him she doesn't think so. In the parking garage she makes him promise to take care of Murtaugh. Murtaugh shows up and invites Riggs to dinner again, but Riggs declines. They decide to go out for drinks instead. They come into Murtaugh's house drunk and beat up and raid the fridge when Trish turns on the light. She tells Roger he can't have ribs, so Riggs eats them instead. She turns off the light and leaves.