“Chemical analysis of the regurgitated matter from Mr. Priam’s stomach brought out the presence of arsenic.
“Everything is given a clean bill ― spices, tuna tin, lemon, bread, butter, milk ― everything, that is, but the tuna salad itself.
“Arsenic of the same type was found in the remains of the tuna salad.
“Dr. Voluta was wrong,” said Keats. “This is not a case of ptomaine poisoning caused by spoiled fish. It’s a case of arsenical poisoning caused by the introduction of arsenic into the salad. The cook put the salad in the refrigerator about 9:40 last night. Mr. Wallace came and took it to Mr. Priam around ten minutes after midnight. During that period the kitchen was empty, with only a dim light burning. During those two and a half hours someone sneaked into the kitchen and poisoned the salad.”
“There can’t have been any mistake,” added Ellery. “There is a bowl of something for Mr. Priam in the refrigerator every night. It’s a special bowl, used only for his snacks. It’s even more easily identified than that ― it has the name Roger in gilt lettering on it, a gift to Roger Priam from Alfred Wallace last Christmas.”
“The question is,” concluded Keats, “who tried to poison Mr. Priam.”
He looked at the three in a friendly way.
Delia Priam, rising suddenly, murmured, “It’s so incredible,” and put a handkerchief to her nose.
Laurel smiled at the older woman’s back. “That’s the way it’s seemed to me, darling,” she said, “ever since Daddy’s death.”
“Oh, for Pete’s sake, Laur,” snapped Delia’s son, “don’t keep smiling like Lady Macbeth, or Cassandra, or whoever it was. The last thing in the world Mother and I want is a mess.”