Poirot said, “Let me return for a moment to the home of the Wallaces. In Nancy Ducane’s portrait of Lady Louisa that I inspected so closely and for so long, there is a blue jug and bowl set. When I walked up and down the room and looked at it in different lights, the blue of the jug and bowl remained a solid block of color, bland and uninteresting. Every other color on that canvas changed subtly as I moved around, depending on the light. Nancy Ducane is a sophisticated artist. She is a genius when it comes to color—except when she is in a hurry and thinking not about art but about protecting herself and her friend Jennie Hobbs. To conceal information, Nancy quickly painted blue a jug and bowl set that was not formerly blue. Why did she do this?”

“To paint out the date?” I suggested.

“Non. The jug and bowl were in the top half of the picture, and Nancy Ducane always paints the date in the bottom right-hand corner,” said Poirot. “Lady Wallace, you did not expect me to ask to be shown round your home from bottom to top. You thought that once we had spoken and I had seen Nancy Ducane’s portrait of you, I would be satisfied and leave. But I wanted to see if I could find this blue jug and bowl that were in the portrait, and painted with so much less subtlety than the rest of the picture. And I did find them! Lady Wallace seemed to be puzzled because they were missing, but her puzzlement was a pretense. In an upstairs bedroom, there was a white jug and bowl set with a crest on it. This, I thought, might be the jug and bowl set in the portrait—yet it was not blue. Mademoiselle Dorcas, Lady Wallace told me that you must have smashed or stolen the blue jug and bowl.”

“I never did!” said a stricken Dorcas. “I ain’t never seen no blue jug and bowl in the house!”

“Because, young lady, there has never been one there!” said Poirot. “Why, I asked myself, would Nancy Ducane hurriedly paint over the white jug and bowl with blue paint? What did she hope to hide? It had surely to be the crest, I concluded. Crests are not purely decorative; they belong to families, sometimes, or, at other times, to colleges of famous universities.”

“Saviour College, Cambridge,” I said before I could stop myself. I remembered that just before Poirot and I had left London for Great Holling, Stanley Beer had referred to a crest.