“How do you know?”

“Did you see her?” broke in Sandy, astonished.

“I did not see her,” Miss Serena replied to Sandy while she answered the older man’s question in the same breath. “But I saw a glimpse of dress just afterward.” Her expression showed confident assurance.

“Why, Miss Serena!” Jeff was stunned. “I didn’t know you was one of these-here detectives.”

“I’m a woman and I use my eyes,” she responded quietly. “A woman needs only to catch a flash of a dress to identify it. Mimi’s maid’s outfit has a distinctive cap—and I saw her cap just as she turned into the after cabin—I was on the bridge. I went there immediately but she had gone out through the galley door and I could not locate her.”

“Why didn’t you tell me?” her cousin demanded.

“There was no need. She had taken only the imitations—the ones you found.”

“But she knew them,” objected Dick. “She wouldn’t throw over the wrong ones and she couldn’t get the right ones.”

“She threw over both sets!”

The Sky Patrol gasped in unison. So did all the others.