By the time we reach Act IV scene i of Much Ado About Nothing, we have already seen ample evidence that Leonato is a rather suggestible, weak-minded individual. When Claudio jilts his daughter at the altar, calling her a "rotten orange" who "knows the heat of a luxurious bed," Leonato immediately accepts all the accusations made against her and wishes she were dead.

Fortunately for Hero, Beatrice and the Friar both believe her and the Friar suggests a plan. He says that Leonato should pretend Hero is dead, having expired in shock at the false accusations made against her. Claudio will then recall how much he loved her and will be smitten with remorse at being the cause of her death. While he grieves over her, Leonato and his friends will have time to find out whether the allegations against her were true or not.

Benedick adds his voice to the Friar's, approving this plan and Leonato agrees, saying:

Being that I flow in grief,
The smallest twine may lead me.

The Friar believes Hero, wants to help her and is playing for time. His reasons for proposing that Leonato should pretend Hero is dead may be exactly as stated. Even if they are not, however, he has had every opportunity to observe Leonato's vacillating nature and must realise that his anger against Hero will not last long. Time is the main commodity needed to solve the problem and the Friar's plan provides it.