Item #: SCP-2551
Object Class: Keter
Special Containment Procedures: SCP-2551 is to be remotely monitored at all times by a permanent staff of at least ten surveillance personnel trained to identify SCP-2551 induction events. Simultaneously, the LETHE algorithm1 is to be run on all feeds at all times. Facial recognition software is to record images of all individuals entering or leaving SCP-2551 for matching to and identification of SCP-2551-1 instances.
If an induction event is identified, either by personnel or by algorithm, the associated individual is to be intercepted before leaving SCP-2551. Method of interception is arbitrary, but must involve breaking the individual's line of sight. For examples, see appendix 2551-C.
Under no circumstances is SCP-2551 to be continuously empty of people for more than twelve hours. In the event that SCP-2551 has been continuously empty for more than eight hours, at least ten individuals not familiar with the effect2 are to enter SCP-2551 and patrol the space until it is declared safe by a member of staff with level 4 or higher security clearance.
Large gatherings of people (including but not limited to: festivals, parades, outdoor markets, public performances and protests) are to be prevented from taking place in SCP-2551, without preventing access altogether. High profile individuals such as politicians and performers are to be prevented from entering SCP-2551 where possible.
All local calls to emergency services are to be passively monitored. On the occasion of a report matching the description of an instance of SCP-2551-1, the call is to be traced and the instance contained, with appropriate distribution of class-C amnestics to witnesses, and destruction of any physical evidence of the effect.
Contained instances of SCP-2551-1 are to be processed on a case-by-case basis. For details, see appendix 2551-A.
Description: SCP-2551 is an urban plaza, known locally as ████████ Square, in the city of ██████████, ██████. Interviews with local residents and testimonies of on-site personnel show that individuals within SCP-2551 display an above average likelihood of misrecognition of passing individuals as acquaintances ("recognition events"); usually as intimate friends or family, but occasionally as peers, superiors or well known public figures. Recognition usually occurs in peripheral vision only, being dispelled upon direct inspection.
In approximately 0.5% of recognition events, the affected individual will stop what they are doing and follow the misrecognised individual ("induction events"). This response is entirely impulsive and involuntary. If distracted in some way before leaving SCP-2551, the individual will resume normal behaviour, with no memory of the incident. If the individual exits SCP-2551 and is not under direct, active surveillance, they will vanish. They will reappear between 12 and 36 hours later, usually in their own home, as an instance of SCP-2551-1. Individuals have never been observed between disappearing from SCP-2551 and reappearing as SCP-2551-1, and have no memory of where they were during this time.
SCP-2551-1 are physically and psychologically identical versions of individuals affected by SCP-2551 induction events, differing only in that they are unable to be acknowledged as human by other living creatures. They are often described as "unnatural", "inhuman", "artificial" or "wrong". When pressed for details, the eyes, skin or bodily proportions are most often identified as appearing different, despite being measurably identical to before being affected.
The effect extends to direct communication of SCP-2551-1 (e.g. voice, handwriting) and to recordings (e.g. photographs, videos) but not to indirect communication (e.g. text typed on a computer) or automated measurements (e.g. facial recognition software). Instances of SCP-2551-1 are not immune to their own effect, and will typically reject their own body. The resulting dysphoria has been observed to cause severe emotional distress.
If SCP-2551 is empty for a prolonged period of time, it will demanifest from its current location and manifest in another, similar location elsewhere. This is known to have happened on three occasions. On each occasion it has relocated to a larger, more populous area.
Despite over 25 years of research, the mechanism of action of SCP-2551's effect remains unknown, and no progress has been made in "curing" SCP-2551-1, preventing induction events from occurring, or causing the effect to demanifest without manifesting elsewhere. The following has been ascertained:

Recognition and induction events occur more frequently in poor visibility conditions (e.g. rain, fog, darkness).
Recognition and induction events occur more frequently in crowded conditions.
Some individuals are significantly more susceptible to the effect than others. If an individual is successfully intercepted from an induction effect, the probability of the same individual being affected by another induction event within the next six months is approximately 65%.
Individuals affected by induction events are statistically more likely to show introverted and depressive traits.
The individual who is misrecognised in an induction event has consistently proven to be completely unanomalous, and to bear a general resemblance to the individual they are mistaken for.
Interception of induction events does not appear to affect rate of future recognition or induction events.
Frequency of recognition and induction events does not appear to be significantly increasing or decreasing over time.
Familiarity with SCP-2551 does not confer any immunity or resistance to its effect.

Appendix 2551-A - Processing of SCP-2551-1 Instances: Due to the number of instances, distress caused by the effect, and inability of rehabilitation, SCP-2551-1 instances have proven difficult to process in an effective, humane manner. Over the 25 years of containment there have been six different site directors overseeing SCP-2551, each of whom has advocated different procedures. The current procedure, created with the aid of the Ethics Committee, is as follows:
Contained instances are to be debriefed on the nature of SCP-2551's effect, including its permanence. They are then to be offered voluntary euthanasia, with a period of 24 hours given to reach a decision. Those who choose not to be euthanised are to be stored in standard humanoid containment cells in Site 22. They are to be provided with loose fitting clothing capable of concealing the entire body, and are not to be exposed to reflective surfaces.
SCP-2551-1 instances comprising former Foundation employees and, at the site director's discretion, other contained instances, may be assigned clerical work requiring no greater than Level 1 security clearance.
There are currently 79 SCP-2551-1 instances in containment.
Appendix 2551-B - Incident Log:

██/██/██: SCP-2551 effect discovered in the town of ██████, ████.
██/██/██: Effect located to St. █████'s █████, near the centre of the town.
██/██/██: Containment established. All civilians excluded from SCP-2551 under the pretext of emergency roadworks.
██/██/██: Containment lost. Effect lost after approximately 24 hours of SCP-2551 being empty.
██/██/██: Effect located to ████████-████ in the city of ███████, ███████.
██/██/██: Containment established. All civilians excluded from SCP-2551 under the pretext of terrorist threat.
██/██/██: Containment lost. Effect lost after approximately 12 hours of SCP-2551 being empty.
██/██/██: Effect located to ████ ████████ in the city of █████████, ██████.
██/██/██: Containment established. All civilians excluded from SCP-2551 under the pretext of quarantine of an infectious disease. SCP-2551 populated entirely with D-class personnel, allowed to freely enter and exit SCP-2551 via one exit leading only to temporary D-class barracks.
██/██/██: Containment lost. Effect lost after approximately 96 hours of SCP-2551 being populated only by D-class personnel.
██/██/██: Effect located to ████████ Square in the city of ██████████, ██████.
██/██/██: Containment established under current special containment procedures.
██/██/██: LETHE algorithm instated. Proportion of induction events identified increased by more than 35%.
██/██/██: At ██:██ local time, all on-site surveillance personnel simultaneously affected by an induction event, being found as SCP-2551-1 twelve hours later. Personnel all report seeing and following Dr. ████████3 out of the main entrance. To date, this remains the only known instance of SCP-2551's effect affecting multiple persons at once, or operating outside of the bounds of SCP-2551 itself.
██/██/██: Containment reestablished.

Footnotes
1. A piece of software trained to identify recognition and induction events based on facial and bodily cues. For further information, including rate of success, version history and source code, see appendix 2551-D
2. Local residents are to be encouraged to participate where possible. Otherwise, D-class personnel may be used. In emergency situations, all but one local surveillance staff are to self-administer amnestics and do as instructed.
3. Site director at the time.

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