In the Serious Side Effects gig, you will need to make your way to the Dewdrop Inn to recover some Beta Acid that was stolen from the fixer’s client. This is easy to do, as you just follow the waypoint to the motel.
When you get you will have two missions. The main mission is to recover the Beta Acid, while there is also an optional mission to find a man called Booker Updike. If you go in the front door and speak with the receptionist, you can get a room for just 50 Eddies, leaving you free to walk around the Inn.
Sneak into the room just behind reception and you will find a gang member sitting at a desk. Snap his neck, then look in the computer beside him. You will find a quest list that tells you that Booker Updike is in room 103. Leave the room and go through the door on the left, then make your way to 103. If you have a Technical ability of 12 or more you can pry open the door.
If not, speak with the maintenance worker in the hall. People with a high enough Body score can intimidate him, while other players can just bribe him to open the door. Inside you will find Booker, who has passed away, seemingly poisoned in his sleep by fumes from the ventilation system.
Now, head upstairs to room 203. Don’t go all the way down the hall, as you can’t open the door to room 203. Go into room 200, where some clueless customer watching a BD is. Go out onto the balcony, then jump across each balcony all the way to the end. Crouch so that you are in stealth mode, then quietly take out the first guard on the left, then the guard on the right, and finally the guard at the end of the room. It is important not to fire a weapon in this room, as things might get a little explosive.
Now you can grab the Beta Acid, go back out onto the balcony and jump down onto the street. The drop point will only be 250 meters away, so head there and drop off the Beta Acid to finish up the mission.