Gibbs gaped like a fish out of water.

"I didn't kill Landry," he finally managed.

"Well, neither did I," Tony said, looking up to find Abby sweeping into the chilled air of autopsy with a smile on her face and a bagged K-Bar in hand.

"Landry did," she said, beaming.

"Did what?" Gibbs asked.

"Killed Landry," Abby said, still grinning. She held up the knife and walked up to Ducky. "I realized something. The knife wasn't wiped—it was a case of too many prints instead of the usual no prints. If 'the killer' had stabbed Landry," she said, making one-sided finger quotes and putting the knife to Ducky's chest, "then his prints would have been on the sides of the handle, here. Or if he had shoved it in, palm on the hilt, like this, then 'the killer's' palm print would have been on the bottom of the handle. And they were. I mean, it was. Except that 'the killer' was Landry—whose palm print I found on the bottom of the handle." She flipped the knife around, placing the point against her lab coat, her palm against the bottom.

"He killed himself," Ducky said, looking from Gibbs to Tony. "That's why there were no punches to his face—he didn't want to risk fresh damage to his knuckles. He tried to frame you for his own suicide, Anthony."

"It's why he turned the AC down," Gibbs said, seeing Tony's pale face and pushing him gently into Ducky's chair. "You told him you had an alibi, and he was trying to mess with it."

"It also solves the mystery of the blood wiped from the doorframe," Ducky said, knowing he couldn't fuss over Tony's stunned trembling without making it worse. "He was trying to hide the fact that the damage to his face was self-inflicted."

"I knew he moved the photo," Tony said slowly.

And Gibbs realized he had been wrong about that—wrong about a lot of things. He knew an apology was going to be necessary, but he didn't think Tony was in any shape to hear it right now.

"It's why he left the ring on the desk," Abby said quietly, her eyes on Tony's wide ones.

But it was Gibbs who spoke. "You wiped Tony's prints from that ring," he said, no accusation in his voice, only understanding.

Abby didn't get a chance to respond, because Tony was suddenly on his feet, his free hand on her shoulder, gripping tightly. "Why did you do that, Abby?" he asked, sounding strangled. "How could you risk—"

"Hey," she said softly, reaching up for his hand. She moved him back to the chair and made him sit before kneeling in front of him, still holding his trembling hand in hers. "Because I know you didn't kill him. Hell, Tony, I knew that even before I could prove it."

Ducky gave a soft smile—and pretended to ignore Gibbs'—at the strength of the bond between the two in front of him.

But Tony still looked sick. "But Abby," he said, his voice barely audible. "You can't prove that I didn't."

She sighed, still squeezing his hand. "As a scientist, I will now say that you're right," she said, giving him a lopsided smile. "Because you cannot prove a negative. But I'm not talking as a scientist right now, Tony. I'm speaking as your friend. You didn't kill Landry. I know that—because I know you. And that's all the proof I need."

She reached up to kiss his cheek and was shocked when he stood, all but running away from her gentle touch.

"Don't, Abby," he said harshly. "I may not have stabbed him, but he's still dead because of me. If I hadn't gone there and rubbed in his face what he did to his son, he would still be alive. I deserve whatever's coming to me."

"Anthony," Ducky scolded, beating Gibbs by a half-second. "Suicide is not something one does on a whim. He must have been seriously considering it to actually go through with the act that night. And his son's death by his own hand would be the more likely motivator—no matter what you said to him."

There was hope in Tony's eyes at those words—and a strong dose of skepticism, too.

But then Abby spoke up. "You guys never hear me out, you know that? I wasn't done yet," she said, reaching into her lab coat and pulling on gloves. She then pulled a small leather-bound book from her other pocket and flipped through several pages. "I was so busy with prints and fibers that I didn't have time to do more than glance through this. But then I really started reading it. Listen. 'I did it again tonight. I hurt my boy. I can't even explain why I do it, but I know I have to stop. But I just can't. I know there's one way to end it all, but I'm too much of a coward to do it. Not tonight. But someday I will. And Brian will be better off without me.' "

She closed the book and blinked tears out of her eyes. "There are at least twenty entries like that one." She looked at Gibbs. "When you cancel Walsh's interview tomorrow, you should tell him it wasn't just his call to Social Services that drove the boy to kill himself."

Ducky nodded knowingly. "You found Brian's prints on that diary, didn't you?"

She nodded solemnly, the implications of that too much to give voice to right then.

Tony was the first to break the silence, his gaze moving from Abby to Ducky and finally landing on Gibbs when he asked, "Is this enough? To prove I didn't kill him?"

And Gibbs knew what he was being asked. "I know you didn't kill him, Tony," he said, watching relief flood the tired green eyes watching him so intently.

"I know it, too," Abby said. "And not just because I believe in you, Tony. The last entry in the diary reads, 'I couldn't stop. I couldn't save him. But maybe God will grant me mercy so I can be with him.' "

Gibbs looked from the book to Ducky. "Why would he admit to killing himself if he was trying to frame DiNozzo?"

But Abby answered first. "He was drunk as a skunk, Bossman," she said, shrugging. "The handwriting's all shaky, but it's definitely his—see the little squiggles on the 'A's?"

"It is also not a blatantly written 'I'm going to kill myself tonight,' " Ducky said. "Perhaps he didn't realize the finality with which those statements resound." He turned to face Tony, putting a hand on his bone-white cheek. "Listen to me, Anthony. While I am not certain that I agree with your decision to teach the man a lesson, you have to know that you are in no way responsible for his death. He is the one who made the decision to plunge that knife into his chest—no one else. Do you understand me?"

Tony nodded mutely, still looking positively ill. And Ducky could understand why—he still had Jethro's admission of murder ringing loudly in his ears, too. But now was not the time to deal with those questions.

"Now, with our mystery solved at this late, late hour," Ducky said. "I believe we should get ourselves some rest—for tomorrow will bring new challenges, new mysteries, and also the wrapping up of this one. Go on, all of you. And someone see to it that Anthony gets home safely."

"I got him, Duck," Gibbs said, a firm hand under Tony's good arm as he helped the trembling agent to the door.

Tony wished he could blame his shakes on pain, exhaustion or the pills he had downed with Gibbs' coffee earlier. But he knew he couldn't. He also couldn't figure out why he seemed to be the only one thinking clearly. While he figured they thought he was safely off the hook for Landry's murder, he couldn't help shivering as he looked back at the stack of photos on Ducky's shiny table.

He knew it would only be a matter of time before the evidence surfaced that they all seemed to have forgotten.