Félix Otto Cadras was born on 4 March 1906 in Calais, Pas-de-Calais, where his family lived in the Pont-du-Leu district.

[2] Félix Cadras was educated at the École Franklin on the Rue Van Grutten, then the EPS on the Place de la République.

He enrolled in evening classes at the Calais École d’arts décoratifs, where he earned a diploma as a lace designer.

He was appointed editor of Enchaîné, the communist newspaper in the departments of Pas-de-Calais and Nord, and became one of the PCF secretaries for this region.

[2] Cadras became a member of the regional committee of Nord, and attended the national PCF conference in Ivry in June 1934.

[4] Charles Tillon and Marcel Gitton gave Cadras the job of organizing and agitating in Calais, Boulogne-sur-Mer and Dunkirk in the 1933–35 period.

He attended the PCE regional conference in Lille on 11–12 January 1936, where his speaking ability impressed Maurice Thorez.

[4] With the outbreak of World War II (1939–45) Cadras was mobilized on 4 September 1939 as an artillery sergeant and assigned to the garrison of Boulogne-sur-Mer, where he remained until the German invasion in May 1940.

His sister Georgette[b] found him there and told him the underground leadership of the PCE wanted him to help organize the resistance in the southern zone.

[7] A failure in security revealed the identities of Cadras and Arthur Dallidet, a member of the PCE leadership staff.

The police broke in and found her throwing a bag of documents through the window, which turned out to describe Resistance efforts throughout France.

[7] Cadras was executed by a German firing squad on 30 May 1942 at Fort Mont-Valérien, Paris, along with Arthur Dallidet, Louis Salomon and Jacques Decour.