He was recruited in England to join the firm of Janion, Green & Company in Hawaii, a successor to Starkey, Janion & Company, formed in 1845. Davies arrived in 1857 but returned to England in 1862, where he stayed until 1867. He then returned to Honolulu, to bail out Janion.
By January, 1868, Davies controlled the business and it was being operated as Theo.
H. Davies and Company. Under the laws of the Provisional Government, it became Theo H. Davies & Company, Limited, in January, 1894.
lieutenant grew to become one of Hawaii"s "Big Five" sugar firms. He acted as a guardian of Princess Kaʻiulani while she travelled to Europe and the United States.
Davies died on 25 May 1898.
In the 2009 film Princess Kaiulani, he was portrayed by Julian Glover.