Mary Graham's health began to decline, and in the spring of 1792, on the recommendation of her medical adviser, she went to the south of France with her husband and sister. However, during the voyage she died off the coast near Hyères, France on 26June 1792. Her sorrowing husband hired a barge to take the casket to Bordeaux but near Toulouse a group of French soldiers opened the coffin and disturbed the body. He closed the casket and returned home to deposit her remains in a mausoleum, which he built in the churchyard of Methven. Graham would himself be laid in the same tomb fifty years later.