On 6 September 1949, he was drugged and kidnapped while off duty, in the Soviet occupation zone of Germany in East Berlin.

On 6 September 1949, while Cox was in a cafe in West Berlin he blacked out while drinking coffee and was drugged by Soviet agents.

Cox was taken to the Soviet Union where he was convicted and sentenced to 53 years in the Gulag for "espionage, sabotage and subversion".

[2][3] While in Vorkuta Cox was put on a diet of two bowls of water and cabbage soup a day.

The one that interested him most was an Austrian girl named Inge Brenner, who was released in October 1953.

[4] Cox was released by the Soviets due to an amnesty on 29 December 1953 along with US Merchant Mariner Leland Towers.

On January 21, 1954, a board of inquiry determined that private Cox could not be held accountable for his absence.

Shortly after his death his fiancée made a statement to the press that Cox was in good health and "murder is the only explanation".