Brother Theo and his monks came to Babylon 5 early in the year 2260 and applied for permanent resident status. They arrived during an influx of missionaries and other religious individuals from many races, most of whom are converged on Babylon 5 following the "sign" given by Kosh. Theo met Susan Ivanova to talk about their application, explaining their purpose for coming as being there "to listen, and to teach." His order believed the same God revealed himself to all the races in the galaxy in a way they can understand. They wished to understand God better by studying all the religions and faiths of the other races. With all the traffic coming through Babylon 5, Theo hoped they could accomplish this goal in "four or five decades." He chose his companions carefully: all were highly sought after experts in a number of different technical fields. This allowed them to provide services on the station to pay for their living space and their work. Ivanova was skeptical, but considered their application.
Theo's arrival coincided with a mad terrorist detonating bombs all over the station. Ivanova decided to solicit Theo's help to catch the bomber by analyzing many hours of video footage from after each of the bombings. After only a short description, Theo asked her to wait. Eventually, Theo and the monks ascertained one person present at all of them who could not be accounted for (who turned out to be the bomber).
Brother Theo quickly befriended the senior staff. He enjoyed playing chess with Captain Sheridan (and clearly outmatched him). He turned to Sheridan when one of his monks, Brother Edward, was troubled with bad dreams and "false memories." Theo quickly suspected that Edward, unbeknown to anyone else (even Edward) had been mind wiped. He asked Sheridan to confirm this before Edward, fearing for Edward's life and his sanity. The crew was able to confirm that Edward had been "The Black Rose Killer," but had been mind-wiped and presumably killed when the installation caught fire. Unfortunately, Edward learned of this first. In a tearful confrontation with Theo, Edward is completely shaken in everything he believes. Theo begs Edward to come with him, promising they can work things out and the "sins of his former life" are best left in God's hands. Edward cannot bring himself to do this, however, and leaves.
The crew quickly surmises that Edward is being stalked by the relatives of his past life's victims. They locate the vicinity where they were going to take him, and Theo accompanies them as they search for Edward. Theo finds Edward horribly beaten and strung up like a crucified man. He is taken down, but mortally injured. As he lays dying, Edward admits he is scared and asks if there is enough forgiveness for what he has done. Theo replies "always" and administers the Last Rites to Edward, who dies immediately afterwards.
Edward's killer, who proudly admits what he has done, is subsequently mind-wiped. Theo manages to arrange for the man to become "Brother Malcolm," the newest member of the order, a man who will be sent back to New Mellarey for training. When Sheridan meets Malcolm, he is visibly upset and recoils, but Theo reminds him gently that "forgiveness is a hard thing, but something we must all strive for."
Later in the year, after the Earth Alliance declared martial law, Brother Theo managed to arrange some help for Babylon 5 through some of his associates back on Earth. This included a Protestant minister named Will Dexter, a Jewish Rabbi named Leo Mayers, a Muslim Imam named Abdul Rashid and a Buddhist Monk named Mr. Chong. They were able to quietly compile a list of resources and valuable data from all over Earth and smuggle it to the station in the guise of coming for a religious convention. Theo (somewhat reluctantly) allowed Reverend Dexter to use his chapel to hold a prayer service. Despite their obvious friendship, Theo disagreed with Dexter's style of praise, insisting that having heard Dexter sing it "was not what the Good Lord meant when he said 'joyful noise.'".
While it is not clear if any of the other monks are ordained, Brother Theo clearly is shown dispensing the sacraments of Anointing of the Sick and the Holy Eucharist.