While heading down the hidden stairs, Olivia missteps and the whole thing turns into a slide, sending her down into the darkness while the others manage to hold onto the walls. She calls up that she's fine, having landed in something that she can't see. Natasha and Morgan work to restore the stairs, and they and Qing go down to find Olivia. Qing warns her to keep her eyes closed, having seen what she landed in via his spirit scout.
After getting Olivia on her feet and away from the pile of discarded limbs she'd fallen in, they reach another door. Morgan opens it, and they enter Valicross' main lab. There are many of the exotic plants he used, and five coffins. Also there is an iron-clad door that radiates heat.
Using the scout, Natasha describes and odd sort of machine beyond the door: several vats of different powders with sluices to a mixing drum that is suspended over lava. The sluices are held closed by zombies. It doesn't take long to realize this is a bomb designed to go off if the magic of the place was dispelled. The zombies would collapse, the components would mix to form gunpowder and the instability of the surface matched with the heat would detonate it.
Morgan is determined to get the Creen spirit trapped in a crystal above the bomb. Towards that end, Qing works to reanimate one of the 'spare bodies' that he and Olivia uncover in the coffins. He makes a believable spirit that mimics Valicross, and uses it to animate the body and command the dryad to bring them the Creen spirit.