Had Tubman not have gotten sick and been unable to go with John Brown on his hair brained raid you could also add treason. She was able to set Brown up with contacts in Maryland, recruited members and helped raise money for his raid.
Harriet Tubman at best had a peripheral role in John Brown's plans. From the end of February 1858 until May 1858 when Brown travelled to Canada to establish his "rebel" state in exile and issue his provisional constitution, he met with Tubman at her home in St. Catherines on April 4th to discuss his planned invasion of Virginia although according to Brown's son John Jr., the plan to specifically attack Harper's Ferry was not made until the summer of 1859.
Tubman provided Brown with safe routes used by her and the underground railroad and she told him that she would try to recruit escaped slaves living in Canada to join his liberation army.
William S. McFeely in his book
Frederick Douglass, notes that prominent blacks that Brown had been claiming were allies of his plan such as Douglass, Tubman, Henry Garnet and Jermain Loguen, as well as members of the Secret Six, failed to appear at the May 8th inauguration of his rebel government that was held in a black school house in Chatham, Ontario. Furthermore, Tubman did not appear at any future meetings and there is nothing in any correspondence to Brown from Tubman nor anyone else that indicates she would join him in his raid.
David S Reynolds' biography titled
John Brown Abolitionist mentions Tubman in a single short paragraph in regards to Brown's meeting with her in St. Catherines, Canada with no mention of her planning on actively participating in his raid. Likewise, in two paragraphs of Stephen B. Oates'
To Purge this Land With Blood - A Biography of John Brown, the author also mentions Brown's meeting in St. Catherines with Tubman, providing him with contacts and safe routes in Virginia and her agreement to recruit blacks from her community in Canada. Only one author from the five biographies I have of Brown and Douglass and one book of the personal correspondence and letters of Brown (
The Life and Letters of John Brown, Edited by F. B. Sanborn, 1885), suggests that Tubman was supposed to participate in Brown's raid. W. E. Burghardt Du Bois in his bio
John Brown, states "[o]nly sickness, brought on by her toil and exposure, prevented Harriet Tubman from being present at Harper's Ferry."
Du Bois employs footnotes throughout his book but this passage is strangely lacking one if it was based on fact.