|“||Something's coming. This threat... an attack... duty as Director... keep the Bureau safe.||”|
The Hiss invasion was an attack on the Oldest House perpetrated by the Hiss on October 29, 2019. The invasion was catalyzed by FBC Director Zachariah Trench, who used the Slide Projector Object of Power to release the Hiss in order to fight what he perceived to be a threat of takeover by the Hedron. Resulting in the near-total destruction of the Federal Bureau of Control, the invasion also saw the appointment of Jesse Faden as the Bureau's new Director after Trench's apparent suicide.
On September 14, 2002, the Federal Bureau of Control intercepted a major Altered World Event in the town of Ordinary, Wisconsin (AWE-24). The AWE had occurred as a result of the Slide Projector, an Object of Power capable of opening doorways to alternate dimensions. The Bureau took the Slide Projector along with Dylan Faden, one of the individuals involved in the AWE, due to his paranatural abilities and sensitivities. Jesse Faden, Dylan's sister, burned all but one of the slides - Slide 36 - which was acquired by the Bureau. FBC Director Zachariah Trench, meanwhile, took one of the burned slides and kept it to himself.
At the Oldest House, Bureau Head of Research Casper Darling established the Dimensional Research division of the Research Sector in order to study the Slide Projector and the dimension projected through the surviving slide, referred to as Slidescape-36. Dylan, meanwhile, was placed in the Prime Candidate program as Prime Candidate 6 or P6; after he was deemed too unstable and dangerous to become Director, he was locked away in the P6 Cell in the Panopticon. At the same time, Darling began to organize expeditions into Slidescape-36, where the Bureau discovered various unidentified resonances, some lethal. In spite of the hazard, Darling pressed on, accompanied by Trench, and the Bureau eventually discovered an entity known as the Hedron, the source of the resonance. Darling removed Hedron from its home and moved it to a chamber in Dimensional Research, where he began to study it.
Meanwhile, Trench had begun to grow paranoid of Darling and Hedron, believing Hedron's resonance posed a major threat to the Bureau. During one of the expeditions, Trench was exposed to a mysterious new resonance, the Hiss, a viral interdimensional force. Recognizing the forthcoming threat of the Hiss, Hedron communicated with Darling, who began to create Hedron Resonance Amplifiers (HRAs) to protect Bureau agents from hostile resonance. Believing this to be a sign that Hedron was taking over the Burerau, Trench took drastic action. On October 29, 2019, Trench used the Slide Projector to open a portal to the dimension represented in the burned slide he had kept from Ordinary, through which the Hiss entered the Oldest House. He then apparently used the Service Weapon to commit suicide.
The Hiss immediately spread its resonance across almost the entirety of the Oldest House, possessing any agents not wearing the protective HRAs, as well as two members of Trench's management team, Tomassi and Salvador. Darling retreated to the interior of the Hedron chamber, and apparently used it to leave Earth's dimension; his whereabouts remain unknown. The building was placed under total lockdown, with the sectors cut off from one another. The Hiss corrupted numerous Altered Items and Objects of Power, which breached containment and spread throughout the building. Dylan, meanwhile, fell under the Hiss's influence and embraced it, considering it to have freed him from the Bureau.
At the same time, Jesse Faden arrived at the Oldest House after receiving a calling from the Hedron through the resonance of Polaris. She found Trench's corpse and bound to the Service Weapon after being chosen by the Board through an Astral Plane ritual. She proceeded to reunite the surviving members of the Bureau, using a Directorial Override to open up the closed sectors. Dylan voluntarily turned himself in after escaping from the P6 Cell in the Panopticon, and told Jesse that the Slide Projector was the source of the Hiss. Jesse entered the Prime Candidate program and learned of how the Bureau had taken the Projector from Ordinary, then, with the aid of Ahti's cassette player, navigated the Ashtray Maze and reached the Hedron chamber. Jesse found Hedron under attack by the Hiss and attempted to save it; however, Hedron was destroyed, and Jesse nearly succumbed to the Hiss as Polaris's resonance faltered.
However, Jesse was able to rediscover Polaris and become the new source of her resonance, saving the Bureau from being destroyed as the HRAs temporarily malfunctioned in the wake of Hedron's death. During the malfunction, Dylan escaped and entered the Astral Plane, attempting to aid the Hiss in taking over the Board. Jesse found the Projector in the Nostalgia Department and entered the Astral Plane, confronting Dylan and cleansing him of the Hiss, causing him to fall into a coma. With the Slide Projector deactivated, Jesse and the Bureau resolved to continue fighting the Hiss until the Oldest House would be safe to remove from lockdown.