The Jewelled Arrow by S.M. Mitra

As Sringa-Bhuja followed the servants, Rupa-Sikha managed to whisper to him, "Beware! await a message from me! " When he had bathed and was arraying himself in fresh garments provided by his host, waited on, hand and foot, by servants who treated him with the greatest respect, a messenger arrived, bearing a sealed letter which he reverently handed to the prince. Sringa-Bhuja guessed at once from whom it came; and anxious to read it alone, he hastily finished his toilette and dismissed the attendants.

"My beloved," said the letter -- which was, of course, from Rupa-Sikha -- "My father is plotting against you; and very foolish were you to promise you would obey him in all things. I have ten sisters all exactly like me, all wearing dresses and necklaces which are exact copies of each other, so that few can tell me from the others. Soon you will be sent for to the great Hall and we shall all be together there. My father will bid you choose your bride from amongst us; and if you make a mistake all will be over for us. But I will wear my necklace on my head instead of round my neck, and thus will you know your own true love. And remember, my dearest, to obey no future command without hearing from me, for I alone am able to outwit my terrible father."