He embarked for India on 28 September 1887 at Liverpool port, in the company of other seven missionaries. He worked among the Khasi people in Shella, a town in East Khasi Hills. He was an ardent evangelist, learning Khasi language, composing hymns in Khasi, and travelling on foot to remote villages. Williams composed several hymns in Khasi, and a rather good singer, Khasis gave him an epithet "the sweet singer of Wales." As an editor he published a quarterly journal "U Nongkit Khubor" (Khasi for "The Messenger") in 1889, the first periodical in Khasi language. Although Williams was a missionary among Khasis, his most historically notable work was his visit to Mizoram (was then Lushai Hills). The Mizos had never been visited by any foreigner (except for punitive British military expeditions in 1881 and 1889 to subjugate tribal warfares and raids on British plantations, which eventually led to British rule of Lushai Hills). In early 1891 Williams met Mizo prisoners, the tribal chiefs, at Sylhet jail who were imprisoned after their defeat in the British expedition. Curious of their unexplored life and fertile land for mission work, he sent information of his plan to Revd Josiah Thomas, Mission Secretary at Liverpool, on 7 February 1891, as below:   His plea was approved by the Shella Presbytery on 15 February. He left Shella on 18 February (Wednesday) and spent the following Sunday at Sylhet. He met Benjamin Aitken, an elder of Free Church of Scotland and sub-editor of Calcutta-based newspaper "The Englishman", who volunteered to join him in his expedition. His frequent companion Kasinath, a young Assamese Christian who was preaching that afternoon, and one Khasi Christian U Khanai also joined him. On Monday 23 February the four set sail on a boat on Surma River, preaching to people along their journey. They spent Sunday 1 March at Silchar and moved the next day. On the third day they arrived at Jhalnacherra and spent a night at Alexandrapur tea garden where Mary Winchester was kidnapped by Mizo Warriors in 1871, the origin of British encounter with Mizos. On Thursday they continued their journey and after a week on Tlawng River, they reach Guturmukh ("Kutbûl Kai" in Mizo), a British telegraph station at the Tut River junction, on 11 March.