Jack Stone is a member of the Office of Secret Actions, or OSA. He is also B.J. Blazkowicz's handler in his mission to stop Deathshead from releasing the Dark Army.
Jack contacts B.J. by radio on the latter's mission to stop Deathshead's plans. He later warns B.J. of a mercenary group infiltrating the base before it starts collapsing.
Jack will appear in Downfall.