The Murder on the Links by Agatha Christie

What the next development of the conversation would have been, I cannot say, for at that moment the door was thrown violently open, and a tall young man strode into the room.

Just for a moment I had the uncanny sensation that the dead man had come to life again. Then I realized that this dark head was untouched with grey, and that, in point of fact, it was a mere boy who now burst in among us with so little ceremony. He went straight to Mrs. Renauld with an impetuosity that took no heed of the presence of others.