The echoes of departed spirits often show up on camera when those in shot were unaware of their presence.
But, as this spine-chilling video shows, sometimes the undead are more than capable of making their presence felt.
It purports to show the startling moment that a phantom pushes a man to the floor before seizing hold of his leg and dragging him along a deserted corridor.
But just as it seems the demonic entity is about to drag its no-doubt accursed victim to the deepest pit of hell, it lets go and vanishes, as mysteriously as it appeared.
The minute-long clip, which emerged online, shows footage of unknown provenance shot on a CCTV camera which captures a hoodie-wearing gentleman striding purposefully along a deserted corridor.
With few signs of life in the stark, clinical-looking corridor, it is already an eerie scene, but hardly looks like the kind of place where the dead might visit.
The clip is silent, presumably since the surveillance camera on which it was shot has no microphone. As the man reaches the end of the corridor a forbidding shadow-like apparition materialises ahead of him.
His previous confidence evaporates as he is knocked to the ground by the spectral assailant. Before he can react, it snatches hold of his left leg, dragging him along on his back.