The green fire spat the party out into a cabin deep in the woods, far from McGonagall's office. As they got their bearings, Finlay wandered up to a bighorn sheep's head mounted on the wall and it began to talk to him. Coaxing the panicked thing quiet with a scratch behind the ear, they learned his name was Fredrickson, and promised that if he stayed silent they would free him from the cabin and carry him back to Hogwarts.
Otto dug through the backpack taken from the Vane Vault and found provisions, what looked like a magical tent, and a strange brass contraption resembling an ancient protractor. On the couch lay a note: "Keep watch, we do not know exactly when they will use the network." Fredrickson mentioned he had heard noises from below, and a search turned up a hidden door and a stair leading down.
The cellar was a dungeon. Crystals of many colors glowed along the walls, and a pile of bones lay heaped at the end of one hall. Two Inferi clawed their way upright and fell on the party. They were tough, relentless things, but fire undid them, Otto and Finlay falling into a vicious Infernus-and-Cerebral-Incendio rhythm that burned them to ash. Deeper in they found more crystals and a potion lab whose ledger, as far as Otto could decipher it, dealt in Floo crystals brewed with blood.
Then they reached the cells. Blood stained the floors, and amid it Caoimhe and the others spotted a pair of distinctive pointed glasses belonging to none other than Callum's mother's. Callum broke down, frightened and weeping. Fredrickson told them what he had seen: Morgana and Nyx had taken Callum's parents away only a few days before.
There was nothing left to find. They gathered Fredrickson and slipped out into the trees. A voice rose from the dark of the forest, and rather than fight it the party reasoned with it, swearing they would free the woods from Morgana's grip. The spirit was reluctant, but in the end it believed them, and pointed them the way out.