History Museum (part 1)

Your teammates will lead you to a locked door on the far side of the loading dock. Turn around and blast the wooden crates on the opposite wall to find a power box you can interact with, which will unlock the door.

Follow your teammates through into a room with a shipping crate hopping around--break it open with a few blasts of your Proton Stream to reveal the museum's curator, who'll summon a nearby elevator. Unfortunately, a ghost seems to have caught a ride on it and will possess Ray! Blast him with your Slime Blower to free him of the ghost, then capture the ghost like you have so many times before.

After the cutscene, you'll wind up in a large room where many of the guests have been possessed! Like before, hose them down with your Slime Blower to expel the spirit. Because the ghosts can repossess someone after being freed, it's best to free only one at a time, capturing them before moving on. As for the capturing process, it seems most effective to wear them down using the Shock Blast from close-range. Oh, and beware that your fellow Ghostbusters can also become possessed--be sure to free them so you have an ally to heal you if you go down.

With the room cleared, follow your team through the hall. You'll face numerous mannequins who've come to life, but they're weak and will go down after a few Shock Blasts. Because the hall has several turns, you can use the walls before each for cover if you need to recover some health.

Eventually, you'll wind up in a long room with a temple in the back. Blast the mannequins along the way, holding back if you need cover. As you approach the temple, target the enemies from the ramp leading up to it, allowing you to easily retreat back down. Once you've cleared the main enemies, use your Blast Stream to take down the flying skulls. When finished, exit through the doors on either side of the temple and follow your team through some more hallways. Of course, you'll face more mannequins, but it's nothing you can't handle.

Before long, you'll arrive at a closed gate. Hang tight while Ray gets it open. Up ahead is a large exhibit dedicated to the Civil War--can you guess what kind of ghosts you'll soon be facing? As you try to exit the room, said ghosts will materialize--and they have guns too. Luckily, the short hall leading you're in now is perfect to battle them from, as it provides perfect cover from their attacks. Like usual, use the Shock Blast for any nearby ghosts, but switch to your Blast Stream for the far away ones--just remain in the short hall until you've captured most of the ghosts. With the room cleared, exit via the door you originally tried going through.