She drew a deep breath. "Ah," she whispered, "that explains the disappearance of Da Costa. He was watching the house, and he was to write to Guarez every day. We have heard nothing."
I gave an exclamation of surprise. "By Jove!" I cried, "perhaps Milford's—"
A sudden sound of voices outside pulled me up abruptly. Instinctively, I whipped my hand to my pocket, and for a moment we stood there in absolute silence. Then came the noise of footsteps, followed almost immediately by a remark in a man's voice, and the little trill of a woman's laugh. I recognised the latter at once, and in a flash I had made up my mind.
"Come, Mercia," I whispered quickly. "It's two of our own party from Ashton. We must see this through. Leave it to me to explain."
She made no answer, and we stepped out through the doorway into the sunshine.
About ten paces away, York and Lady Baradell were coming up the hill towards us. As we appeared in the opening they stopped, and for a moment all four of us stood looking at each other in a prettily embarrassed silence.
York was the first to speak. "Then it was you, Northcote!" he observed. "Lady Baradell declared it must be your car."
"Lady Baradell was right," I returned cheerfully. "Let me introduce you all. Miss de Rosen, Lady Baradell, Captain York."
Lady Baradell, who had favoured Mercia with one swift, incisive scrutiny, smiled sweetly.
"We were walking over to the Cuthberts'," she remarked, "and we happened to see your car standing on the grass. I had no idea you were an antiquary, Mr. Northcote."