H.P. Lovecraft's The Shadow Out of Time

[Professor Peaslee of Miskatonic University has been acting very strange - could he be out of his mind? No his mind is out of him!] Just because one lives in Arkham - just because one teaches there at Miskatonic University, it doesn’t mean one has any interest in the occult - in the abnormal. That was always the view of Nathaniel Wingate Peaslee, a respectable professor of political economy. Until that one Thursday in 1908, when Professor Peaslee suddenly began to see in front of him not his students in their lecture hall, but strange shapes inhabiting a grotesque chamber. He collapsed unconscious, and when he awoke, he was strange, very strange. Seemingly unable to recall his identity, the mind inside the body of Nathaniel Peaslee was oddly uninterested in the person he had been. The psychologists were baffled as he sought not to recover his old memory, but to obsessively study the world around him, travelling to distant lands, reading occult books, disturbing others with his odd perspectives on time and existence. He alienated and frightened people - his friends, his wife, even most of his children, except for his youngest son, who believed that one day Nathaniel Peaslee would come back. And then, in 1913, Professor Peaslee did come back, with no memory of his strange sabbatical, but deeply disturbed by the dreams and visions it left him with. His search for the past five years gone missing from his life will lead Peaslee to other cases of lost identity resembling his and eventually to an ancient city in the Australian desert - from where a long-vanished race still casts their shadow out of time.