It seems obvious that Gerda is the murderer. Henrietta steps forward to take the revolver from her hand, but apparently fumbles and drops it into the swimming pool, destroying the evidence. However, the pistol that Gerda was holding was not the gun used to kill John. None of the witnesses has seen Gerda shoot John. It seems difficult to build a case against any of the other potential suspects. Lucy was the next suspect, as she kept a pistol concealed in her basket of eggs. However, the pistol was the wrong calibre. Henrietta is the next suspect, having left an unusual doodle in the pavilion around the time John was killed. When the murder weapon turns up in Poirot's hedge, it has fingerprints that match none of the suspects.