History Museum (part 3)

Open fire on the large obelisk and descend down the revealed staircase. After your teammates do some yammering, follow Ray through the gate he kicks open and trail him through the tunnel.

Upon emerging onto a walkway, head left first to find a Toy Car artifact, along the wall, then head the opposite direction. Look for a cracked circular covering along the wall, just before the gap. Spray it with your Slime Blower to reveal a tunnel you can now enter. Head on through and follow your teammates to avoid getting lost.

You'll soon wind up in a circular room, where Ray will fill you in on the new Composite Particle System you've been equipped with:

• Meson Collider: This fires a short, but powerful blast at your target. Even better, after hitting your first target, the gun's secondary function (overload pulse) will home in toward that target--nifty!
• Overload Pulse: This is the machine gun of the Ghostbuster's arsenal. It fires a rapid blast stream in a straight line--unless you've already targeted a ghost using the weapon's primary function (Meson Collider), in which case the blasts will home in on that target. Combine both weapons to pack a powerful punch.

Exit the circular room through the gate and continue across the bridge, where you'll find the level's boss. The battle itself is pretty basic, cycling between two portions: the boss-fighting portion, and the minion portion. The first is where you battle the large boss himself. The large, glowing spot on his chest is his weakpoint--you're best off targeting it first with the Meson Collider to lock-on, then lay into him with the Overload Pulse which will now hone-in on his chest. He won't really attack you directly until he's almost out of health, at which point his attacks can be dodged by moving side-to-side; however, it is in your best interest to revive your teammates whenever they go down for the second portion of the battle. Oh, and you may want to shoot the cannisters surrounding the arena, preventing the boss from using them for cover.

Unfortuantely, you won't have much time to attack before he disappears, leaving behind four black-goo portals on the floor, one in each corner. Whip out your Slime Blower and use it on each of the enemy-spawning portals to close them quickly, then take down the enemies they created. The Slime Blower works on the enemies too, though the Shock Blast is most effective, at close range, of course. Once you've cleared out the enemies, the boss will return giving you another chance to attack. Repeat ad nauseam until he goes down.