Das Gesicht auf der Wand

It is an eerie, cold evening, with the wind whistling through the trees. In a remote pub, a few people have gathered around a single candle and are telling each other scary stories. A man from the next table joins them and tells them about a mysterious apparition. An eerie face regularly appears on the wall of his room, giving him the creeps. The stranger recounts in detail how this gruesome occurrence is bringing him to the brink of a nervous breakdown. Whose face is it? Is it that of a dead person?