Silas Deane was a man of promise, he came from humble origins, but he rose to great heights. However, he did fall from respect, and lived out his life thought to be a traitor and a cheat. He died in an unusual manner, however. On the deck of the ship that would bring him back to America for the first time in over a decade, he fell extremely ill and died. Silas Deane was murdered by a certain Dr. Bancroft. This is not definite by any means, but it is the most probable cause of his death. The murder of Silas Deane protected Bancroft, and so shows the motive of the murderer, and his circumstances show his ability to perform the act.
Dr. Bancroft was an American spy and the personal secretary of Deane while Deane was in France working for the United States. However, it is now known that Bancroft was a double agent, actually working for England. Deane knew this as well, presenting a possible danger to Bancroft. Silas Deane remained friends with Bancroft throughout his life, providing Bancroft the ability to make sure that Deane would not decide to sell out his friends to get back under the good graces of the American People by exposing a double agent. However, this would have changed when Deane decided to return to America with the help of his brother. This made it so that Bancroft could no longer watch over Deane to make sure he did not attempt to sell him out. Thus, Bancroft saw it as an opportunity to eliminate the threat entirely.
This is not as improbable as it might sound. Bancroft, for instance, was perfectly positioned for all of this to happen. According to Bancroft himself, he assisted him “with advice, medicins, and money for his subsistence.” These “medicins” as Bancroft puts it, might not be as innocent as they might appear. Bancroft, earlier in his life, published a book about wildlife in the tropical land of Guiana. A large part of that book was the native poisons, and their powers and use. He was known to have brought some back for research, but it is not impossible that some of it may have gone to a more concrete experiment: the death of a certain Silas Deane.
It has been said by some scholars that Deane probably committed suicide. This is highly improbable however, because of his previous good spirits toward setting off to America. He had said in many of letters prior to that voyage how he had envisioned building a canal from Lake Champlain to the St. Lawrence R., and had spent hours working out his plans to build that canal down to the number of workmen, and the amount of time required. Does it not seem odd that he would go to so great an extent to plan his business in America if he never intended to set a foot ashore on America? Also, the circumstances on the boat raise questions about the suspected suicide. When Deane fell very ill, he had just decided to take a stroll with the captain and was speaking to him when he suddenly succumbed to the drug possibly administered to him, or by him. It makes no sense that he would decide to speak to the captain if he were planning on his death, but would more likely stay where he was least likely to receive immediate medical care.
Dr. Bancroft killed Silas Deane. This statement is not provable, as is very little in history, but it is defendable, and supported by historical evidence. Dr. Bancroft was at risk if Silas Deane revealed him to America as a double agent, so providing Bancroft with a definite motive to end Deane if he were to travel to America, or attempt to do so. He definitely could have, having attended Deane a few weeks before his departure, and having written that administered drugs upon Deane, the circumstances are correct. There is little chance that Deane committed suicide: the facts simply do not add up. He had no need to travel to America in the first place if he only meant to end his life. The events that led up to his death make no sense with the line of reasoning that supports the idea of suicide. Silas Deane was murdered; this is not fact, but it is the best conclusion that the historical evidence available can reach.