I read about that incident I think in the Official Records. They were to commandeer a boat, or lease one out of Buffalo as I remember it, but my memory is faulty. Mainly confederate officers were kept there. Some of these may have been transferred down to Morris island when the Yankee prisoners were being used as a shield in Charleston; tit-for-tat about that!There was an attempt to free Confederate prisoners on Johnson's Island by John Yates Beall and 20 Confederate volunteers who operated out of Sandwich ( now Windsor) Ontario , but after seizing a steamship the plan fell apart and they returned to Sandwich . I believe this whole plot was done in secrecy and have never found where Ontario authorities were aware of it .
Rock Island Prison is also on the list of conspiracy plans given to Hooker this go 'round. I believe it is near Chicago.