W.S. Gilbert, The Rival Curates.

In this Bab Ballad the curate Mr Clayton Hooper, finding that he has a rival in mildness in Mr Hopley Porter, resolves to have him assassinated, but later decides to spare him on condition that he lapse into normal behaviour. This suits Porter, who has been looking for an excuse to do just that, very well. The plot recurs in Patience: the pale young curate alluded to in the clue, however, is Dr Daly in The Sorcerer.