The Episcopal bishop of Maine will be on hand next week when the congregation at St. Thomas Episcopal Church, Main Street, celebrates an old friend in a new role. The Rev. Carolyn W. Metzler has been appointed vicar of the congregation, and Bishop Chilton R. Knudsen will install Metzler during a service at 5 p.m. Sunday, Sept. 12. Metzler, who was ordained in March, has served as chaplain at Penobscot Valley Hospital in Lincoln and at The Acadia Hospital in Bangor. She has worshipped at St. Thomas for four years, and as the church explains in its announcement, “It is unusual for a person to become the priest in the congregation that supported her in the ordination process. [Bishop Knudsen] has made it clear that this is not the continuation of an old spiritual companionship; this is a new relationship between priest and people.” Call 736-2010 for information.