SCP: Pandemic is based on the SCP-5000 canon by Tanhony.
The SCP Foundation is a non-governmental organization with a high reign of the prosperity of humanity — while remaining in total secrecy. They were once dedicated to containing and researching anomalous entities of our world, protecting humanity under a shade of moral grey.
The directive of the SCP Foundation made a complete shift upon the discovery of a foreign entity that has infected every human’s psyche. The O5 Council, the leaders of the SCP Foundation, initiated a directive to exterminate the human race in an attempt to stop the nefarious entity from reaching its true potential, undertaking the belief that doing so would be a mercy.
Several members of the SCP Foundation defect and retaliate against the omnicidal efforts, whistleblowing information to other large organizations such as the United Nations Global Occult Coalition (GOC) — near-before and after the remaining high-ranking staff embedded within the SCP Foundation had their consciousness memetically altered to become unempathetic and willing to abide by the directive, low-ranking staff and other staff deemed “unessential” were designated to be killed by security forces.
The directive’s initial plans include targeting civilian populations with artificially engineered entities known as Psi-Z, which is a project actualized by Erwin Koch, one of the leading researchers of Area 12.
Defectors of the SCP Foundation, along with assistance from the GOC, form a fireteam to infiltrate Area 12 in an attempt to prevent Psi-Z from reaching fruition, collect sensitive data, and exfiltrate Erwin Koch for interrogation. The fireteam’s efforts are to impede the SCP Foundation's present and future plans for global omnicide and to find more vital information on the entity behind the psyche-pandemic.
During the GOC's raid on the facility, it experienced a massive site-wide containment breach of Psi-Z and other contained entities. In addition to the existing mission, you must also fight through and survive against the horrors that broke loose.