"Its importance is obvious," Rankine agreed.
"If the boat couldn't carry enough fuel, she'd have to get some while she was out on a trip?"
There was another long pause and then Mrs. Woodhouse spoke.
"You must mean somewhere in Scotland," she said.
"Disagreeable conclusion, isn't it? But we don't know yet that it was a submarine," Rankine answered.
"But suppose there should be an enemy submarine in the North Channel that hadn't much fuel left, how could she renew her supply?" Staffer asked.
Rankine seemed unwilling to talk about the subject, but he smiled.
"Oh," he said, "it's hard to tell. One could form plausible theories, but they'd probably be wrong. Perhaps we'd better leave the matter to the people whose business it is."
He began to talk about something else, and the curious tension that all had felt gradually slackened. Soon afterward, a servant announced that Mackellar had arrived. Staffer had been expecting him, and when he left the room Madge and Dick went to the drawing-room with Elsie and Mrs. Woodhouse, and Rankine found himself alone with Andrew and Whitney.
"Have you made any progress with your investigations?" he asked.