In the short story Greenshaw's Folly, Nat Fletcher is the son of Harry Fletcher and Nettie Greenshaw. He is an actor, currently working in Boreham-on-Sea.
He stabbed Miss Greenshaw in the neck with an arrow.
Miss Marple theorised that Nat actually might be the son of Harry and the woman using the name Mrs Cresswell. The indication was in that case that Nettie's son had died earlier. This theory is however never confirmed.