Clean and Serene

Clean and Serene is the first mission in GTA IV DLC The Lost and Damned.

Overview
In the introductory mission, the main members of The Lost Brotherhood motorcycle club (aka Lost MC) ride to club president Billy Grey's location. He's just been released from rehab and is currently speaking with a parole officer and his sponsor from the drug treatment program. Johnny Klebitz, protagonist of the DLC, hands Billy his old jacket and off they ride.

Walkthrough
Take Billy back to the Lost MC Clubhouse (which also acts as a safehouse for the player, amongst other things). Since Billy is the leader and riding on your back, the other Lost members will ride in formation behind you. Don't total the bike or kill Billy. Don't worry about the following members get seperated from the main group; after a set distance, they will automatically spawn behind you.

In Billy's absence, Johnny has had to run the gang in his place, and with Billy's return, Johnny is relieved of his commanding duties. Already, tension between the two seem to surface, evidenced in a cutscene. Billy demands Johnny for his Revenant bike, which Johnny has sold to pay for Billy's various fees while inside. Eventually, Billy and Johnny move out to the shop which was the last known location of Billy's motorcycle.

Now ride Billy and the Lost to the chopshop in Bohan. Once you arrive, a cutscene plays. The shop owner is reluctant to give up information, but a full-throttle bike tire to the corner of the mouth by Johnny gets him talking. He sold the bike to The Angels of Death (aka AODMC, or simply AOD), The Lost Brotherhood's bitter rivals. To repay the shop owner for this injustice, Billy hits him in the face with a hammer before walking out. Now with a set location, Johnny head there with Billy and other Lost MC members in tow.

Time to get Billy's bike back. Ride again with Billy riding piggyback, and follow the yellow marker to Algonquin. some Angels of Death members are hanging out with Billy's bike. Billy charges in for his ride, and you and the others need to help. With your Sawn-off Shotgun, blast through the enemies and make sure to pick up ammo and extra weapons from fallen enemies. The Sawn-off is exellent at close range, and can put a car in flames in 2 shots. As you kill AOD members, more will arrive. Slaughter everyone, and Billy will reclaim his bike.

Time to amscray. With the President restored to riding status, he will now take the lead of bike convoy, and you must fall back as a regular member. Get back on your bike and follow Billy in formation. The Lost symbol will appear on the group when you are riding in formation, which will start a conversation amongst the member, as well as heal you, give you armor, and repair your bike. Get back to the club to finish the mission.

Trivia

 * During the introductory cutscene for the DLC, while The Lost Brotherhood are riding in formation down the streets of Liberty City, Niko Bellic can be seen walking on the sidewalk in his default attire, bumping into a pedestrian and saying something in Serbian to the person. Throughout the DLC's main storyline, Niko's exploits will be chronicled via the various online news services, such as Liberty Tree, Weazel News, and Public Liberty Online, as well as some dialogue from the cast. For example, early on, Johnny can read the articles of recent "arson spates" in Broker and activist lawyer Tom Goldberg's assassination.
 * Niko's cameo appearance in Alderney is somewhat incongruous, as he would still be confined to Broker and Dukes during this mission of The Lost and Damned.

External Link
Clean and Serene mission on Youtube by GTASeriesVideos.