A valuable tiara has been stolen from a guest bedroom. But the thief didn't make a clean escape: there is a witness and some important evidence left behind. Holmes begins by interviewing the witness, a French lady, Susanne Le Bon.

Holmes: Please be so kind as to tell us what you saw.

Susanne: I didn't see much. You know I have just the one eye. But I tell you what I did see. I was in my room when I heard a scream. I opened my door and saw a tall figure running away carrying what looked like the tiara that was stolen. I couldn't see a face. I don't know who it was.

Holmes: Madame, you may have seen more than you realise. For instance, did the figure move like a man or a woman? Would you say they seemed old or young? Just how much taller than you was the figure?

Susanne: Bof. I don't know. Maybe 10 or 20 centimetres taller than me. I think maybe it was a woman as she was wearing high heels but you never know these days. She moved very well. I think maybe she was younger than me.

Holmes: Thank you Madame. That may be all we need. Watson, do you have the blood group from the blood found by the broken window?

Watson: I do indeed Holmes. A very common group I'm afraid. It is group A.

Holmes: No matter Watson. I think our culprit will be facing justice sooner than she thinks.