Becker, who died just weeks after shooting had wrapped, cast mostly non-actors for the main roles, including one man (Jean Keraudy) who was actually involved in the 1947 escape attempt, and who introduces the film.

The four existing cellmates expect long prison sentences, ranging from 10 years to possibly execution by guillotine, and have a pre-existing plan to escape.

Gaspard quickly gains their trust sufficiently for them to reveal their escape plan: digging a hole through the floor to reach the underground passages.

The bulk of the film then focuses upon their gradual progress, which results in two men reaching an outer manhole in the public street outside the prison walls.

According to the 1964 press materials that are included in The Criterion Collection DVD, Jacques Becker first read of the 1947 La Santé Prison escape attempt in a newspaper.

"[4] The New York Times' Bosley Crowther noted that the non-professional actors "play their roles with such simple, natural force that they become not only bold adventurers but also deeply appreciable friends.

"[5] "As long as men have been placed behind bars" wrote Kenneth Turan, "they've plotted to escape, and those plans have powered prison-break movies without end.

"[6] Whilst praising the film otherwise, Richard Brody of The New Yorker wrote that Becker's "deeply empathetic, fanatically specific view of his protagonists leaves out some elements.