As with other Lovecraftian works, this story features otherworldly alien beings that are not simply variations on humans or other familiar terrestrial animals.

In order to achieve this goal, they transfer their spirit to the respective epoch from which they wish to acquire knowledge, into the body of a suitable person.

Peaslee receives a letter informing him that excavations have been carried out in the great sandy desert of Australia that correspond to what he has written in various articles.

Torn between the desire to escape and a feverish mixture of burning curiosity and impulsive surrender to fate [sic], he descends deeper into the familiar ruins.

S. T. Joshi points to Berkeley Square, a 1933 fantasy film, as an inspiration for The Shadow Out of Time: "Lovecraft saw this film four times in late 1933; its portrayal of a man of the 20th century who somehow merges his personality with that of his 18th-century ancestor was clearly something that fired Lovecraft's imagination, since he had written a story on this very theme himself—the then unpublished The Case of Charles Dexter Ward (1927)."

Lovecraft noted some conceptual problems in Berkeley Square's depiction of time travel, and felt that he had resolved these flaws in his novella.

[5] Other literary models for The Shadow Out of Time include H. B. Drake's The Shadowy Thing (originally published as The Remedy in 1925), about a person who has the ability to transfer his personality to another body; Henri Beraud's Lazarus (1925), in which the protagonist develops an alter ego during a lengthy period of amnesia; and Walter de la Mare's The Return (1910), featuring a character who seems to be possessed by a mind from the 18th century.

Following his reversion to his own body, Peaslee's perception of time, his "ability to discern between consecutiveness and simultaneity", had undergone a subtle distortion.

Peaslee's out-of-body experience has a cost: memories of temporal transportation are accompanied by pain and the sense of an artificial psychological barrier.

He describes experiencing time as a continuous flow, without clear boundaries between past, present and future, as "an awesome, brain-shattering truth [...] beyond normal conception" .

However, Peasey's experience, as outlined in the text, challenges this assumption, presenting time as a chaotic and disorderly process that lacks the familiar concepts of cause and effect, and appears to defy any clear organizational principle.

His journey into the past is incongruous with such a perception; however, his mind must re-establish the psychological delusion of continuous time if he is to function within his usual state.

Consequently, although Peaslee's "mental barriers wore down" over time, eventually enabling him to recall his time-travel narrative, his intellect remains at odds with his psychological understanding of the universe.