Manalive by G. K. Chesterton

A new tenant arrived at Beacon House, a London boarding establishment. He is identified by lodger Arthur Inglewood as an ex-schoolmate named Innocent Smith. During his first day in residence the eccentric Smith creates the High Court of Beacon; arranges to elope with Mary Gray, paid companion to heiress Rosamund Hunt; inspires Inglewood to declare his love for Diana Duke, the landlady’s niece; and prompts a reconciliation between jaded journalist Michael Moon and Rosamund.