Night Shift Pranks

While working as a cleaner in a professional building, the narrator recalls being pranked by a security guard who would watch them on the monitors and occasionally pretend to be a serial killer. However, one night they receive a creepy phone call and assume it's the guard, only to find out that the guard was not working that night. Months later, they witness something unsettling on the monitors and the guard investigates, leaving the cleaner feeling uneasy.