In 1886, with two Jesuit priests, Pascal Tosi and Aloysius Robaut, and one layman, Frank Fuller, he sailed from Victoria with the intention of reaching the upper Yukon. When they reached the confluence of the Yukon River and Stewart River, Seghers decided the other two priests should spend the winter there, while he and Fuller would press on to Nulato. Father Tosi expressed concerns about this proposal, noting that Fuller had displayed signs of emotional instability. Seghers acknowledged the concern, and how the lateness of the season would likely impact his work. He gave as his reasons for going ahead anyway as his wish to fulfill a promise made to the people of Nulato to return eight years earlier, and that there were stories that an Anglican priest, who was allegedly at St. Michael, Alaska, might arrive there and establish himself before Seghers. As they continued down the river, Seghers came to realize that, as traveling conditions and the boat deteriorated, Fuller's mind did as well. On 16 October, he wrote in his diary: "Peculiar conversation with (Fuller) in which, for the third time, he gives evidence of insanity." On 27 November, Seghers and Fuller, with two native guides they had acquired at Nuklukayet, decided to spend the night at the fish camp at what is today known as "Bishop's Rock". Seghers was in high spirits, laughing frequently, thinking that he would finally reach Nulato the following day. Fuller, however, remained sullen, looking suspiciously at his companions and remaining agitated throughout the night.