The Final Clue

"I don't get it," Beckett says. "What are you trying to tell me, Castle?"

Castle stares at her as if she's just admitted to a secret crush on her boss.

"And quit looking at me like that!"

"It's nothing," he finally says. "If the final clue to solving this case equates to nothing."

"What is it?"

"But!" He gestures wildly at the murer board. "It's all right there! I don't know how you can't see it."

"Spit it out, Castle. I don't have all day."

"You don't see it? I tell you the answer now and you'll be kicking yourself for days." He smirks.

Beckett frowns. "Castle."

"It was the mother!" he bursts out.

"Oh!" Beckett's hand goes up to cover her mouth as she scans the board again with her eyes. The scribbled notes and something the mother mentioned earlier finally click into place in her mind. "Of course!"

"See now?" Castle smiles. "Wasn't so difficult, was it?"