Upon a second look at Dean's death, the author arrives at some new conclusions. Did Deane really commit suicide? From Dean's letters and surviving papers the author concluded that Deane believed himself innocent and would not have had any obvious motive for suicide. And even if he did feel guilty for doing something wrong, why would he kill himself ten years after the fact? Why would he wait a week aboard ship to take the poison in? We have no proof that Deane committed suicide, we do not know the circumstances of his death. The report that was made by a captain of the ship was never preserved. His suicide was a suspicion of Dr. Bancroft, his closest friend. He wrote Dean's death account. .
The author suspects that this very Dr. Bancroft was the one who helped Deane die. Deane knew that Dr. Bancroft was spying for Britain, that he was a traitor, a double agent. Deane had too much information about Dr. Bancroft's wrongdoing and Dr. Bancroft got too nervous that all the truth would be revealed. In London Dr. Bancroft could watch Deane but in America he could not. He did not want to loose all his privileges, it was easier for him to get rid of Deane.
Dr. Bancroft did not just murder him. He was an expert on poisons and probably slipped some of it into Dean's laudanum mixture knowing that Deane would not take it until he was on shipboard off to America. He had a good alibi. He was not on a ship along with Dean and he did not see him for more than a week. .
As for me, I agree with the author's suspicion that Deane did not commit suicide but died from a deadly poison given to him by Dr. Bancroft. Why would Deane want to end his life aboard ship if he was going to America in order to start a new life? He had made plans for the future and suddenly killed himself? I do not think this is the case. I think Dr. Bancroft had to do with it. I think, his fear of being busted, of being accused as a traitor helped him make the decision.