Retreat in Trelawny, Jamaica is near Hampstead and (according to Fremmer) both estates were owned by Jane Stone, a slave who became the wife of Jonathan Barnett, the prominent landowner in Montego Bay and the man responsible for catching "Calico Jack" Rackham and the famous two "lady" pirates.
In "Jamaica Surveyed" ( BUY a Copy), Higman reports that both estates were owned by John H. Defell at the time of Emancipation.
Retreat had 180 slaves at the time of Emancipation

The Water Mill was still in operation in 1850, but shortly afterwards, Hampstead and Retreat were consolidated and a steam mill was installed.