Slade was looking for the Null Zone. He had heard that there was a subway train that the Bonegnawers use to get around occasionally (it connects to their homeland) that seemed like it might be travelling through the Null Zone. On the theory that all things are connected, Slade figured if you took a subway train, shifted into the umbra, and jumped out at a service passage, that that service passage might very well be the Null Zone (all of that theory was based on Umbral tidbits he had learned from Sionna and from lots of delusions).
Having already been to visit Hyperion, Slade was carrying everything he thought might help him get to the Land of the Dead and back. He brings an acorn (which he'd been carrying for some time, hoping to plant it in AutoCthonia), plus two coins (as ferry toll in case he winds up temporarily dead), three drugged bunnies and manacles (in case he runs into Cerberus) and some other miscellanea.
Slade and Genni carefully take a subway train that no one else was on nor can see, so "no one" would know that they hadn't been there if it came out the other side of the tunnel under the Bay without them. Slade shifts into the Umbra.
Meanwhile, Chryse eats poison and lies down on a slab of granite to go be dead for a little while -- all part of her Euthanatos training. Her mentors hear someone at the door...
The BART stops at a station under the Bay and milspec goons get on, carrying boxes of hardware. Shuffling corpsefolks get on. ItX goons get off.
[ Either at this point, or a little later, they come to see Chryse's mentors riding the train, and hand one of them the acorn. ]
Someone goes through punching tickets; Slade hands the two coins to the conductor, who punches holes in them and gives them back without comment. Chryse stands out, looking like a tourist, among crowds getting off BART. They meet.
Minos is tossing people into various doorways, or at least telling them where to go. PCs conclude this is bad and try to escape back onto BART. Various demons object; Coyote intervenes and steals the ticket-puncher's cap, causing pandemonium to erupt (er...) During the chaos, Slade and Chryse and Genni sneak back onto BART, and it starts back up, going into a tunnel. Pursuit continues on the train, as demonic BART employees give chase. They leap from the train against the fast-moving tunnel walls and find themselves in the Null Zone, dark hallways with good soundproofing and occasional images appearing and disappearing.
Images appear. Chryse sees her chantry demolished but herself unhurt, and a tree branch waving across field of view. Slade sees Himiitsu talking with his clone. Genni sees a Pentex board meeting [With some shadowy (umbral?) non-human figures observing/attending. Or were some of the board members the inhuman ones?]. All three interest them but they don't try to follow the images out of the Zone.
An image appears below them and they fall in -- to a garbage dump of ItX borgs. Slade interrogates a barely-alive borg who reports an assault on a Vancouver chantry, then dies. The top of the room shimmers and more things fall in. Slade leaps for the roof and is grabbed by a tentacle and yanked into some other dimension. The walls inevitably start to close in. Chryse and Genni search frantically and find an escape hole in the bottom of the pit.
Chryse and Genni find themselves in Auto-cthonia, and escape with Martin's advice (obtained via cell phone: dump a wrapper on the ground and wait, then follow the trashbot that picks up the wrapper); Slade meanwhile watches ItXborgs fight a cthulhoid horror from beyond and sneaks through the gate to reality.
All three wind up in Vancouver. Genni finds herself in a dumpster. Slade finds himself in a tree, after which he has a conversation with a small kid, who mostly gets the better of Slade. Chryse wakes up back in her chantry, where she finds that (a) ItX did in fact attack her chantry and kill her mentors; (b) the borgs are indeed also dead and her body is unharmed, because (c) the acorn that her mentor was handed by Slade grew into an oak tree/vine/horrific thing that impaled and killed the cyborgs.