On the afternoon of Sunday, 12 February 1786, while her employers were away, Dawson collected a large quantity of clothing, jewellery, and money, and left the house.
Here, on 4 January 1787, her death sentence was commuted "on condition of being transported for [a term of seven years], to the Eastern coast of New South Wales, or some one or other of the islands adjacent".
Arthur Phillip, the commander of the expedition, in a letter to Under Secretary Evan Nepean, complained of the condition that the convicts were delivered to the transports: The situation in which the magistrates sent the women on board the Lady Penrhyn stamps them with infamy – tho' almost naked, and so very filthy, that nothing but clothing them could have prevented them from perishing…there are many venereal complaints, that must be spread in spite of every precaution I may take hereafter…[4] Lady Penrhyn rendezvous with the ten other ships that was to make up the First Fleet at Portsmouth.
Governor Phillip decided that this site wasn’t suitable so the fleet moved to Sydney Cove in Port Jackson on 26 January 1788.
In his will, dated four days before his death, he left a yearly sum of £50 to "my dear friend Margaret Dawson, otherwise Henderson ... whose tenderness to me, while in ill health, claims my warmest gratitude and by whom I have had two natural children … and who is now ensient".
With a settled income of £50 a year, and rent from properties in New South Wales, it is unlikely that Dawson would have had to earn a living after Balmain's death.
With the help of his friends she continued to encourage her son John William Henderson's education, and he eventually returned to New South Wales in January 1829 as a surgeon, like his father.