The Investigation (original title Śledztwo) is a science fiction/detective/thriller novel^[1] by the Polish writer Stanisław Lem. The novel incorporates a philosophical discourse on explanation of unknown phenomena.^[1] It was first published in 1958 in Przekrój magazine (issues 698-711) and in 1959 as a book by the Publishing House of the Ministry of National Defense (Wydawnictwo Ministerstwa Obrony Narodowej).

The novel is set in London. A young Scotland Yard lieutenant investigates mysterious disappearances of corpses from London morgues. The only "explanation" is an abstruse statistical theory that correlates the body snatching with local cancer rates. The detective, however, since the very beginning suspects the same statistician being the perpetrator. Reality, however, proves less mundane and certainly less comprehensible than he had hoped. It appears that as if the corpses "resurrect".^[2]

In The Investigation the classic procedural police mystery is turned into a metaphysical puzzle, with Kafkaesque themes. As in almost all Lem's production, philosophical and epistemological questions are presented under the simple surface of the plot: what is the role of scientific inquiry? What does the existence of competing explanations mean for that goal? The novel also introduces a theme that will later be present in Lem's works, in particular, in his major essay, The Philosophy of Chance: that observations are formed by the properties of the observer's mind, rather than by any properties of the observed.

The novel was put on screen in Poland twice: as a TV film (director Marek Piestrak [pl]) (production: 1973, premiere: 1974)^[3] and in 1977 as a TV play (director Waldemar Krzystek).^[