Tony's hand connected with her face with a sickening crunch.

He hadn't known she was there. Using her oft-cited "ninja skills", Ziva had come up behind Tony as they fooled around in the gym, and when he sensed a looming attack he spun around, and the back of his hand complete with knuckles and with the full weight of his body behind it, smacked her in the mouth.

Time slowed as Tony stopped, and Ziva doubled over, her hand to her mouth, blood running down her chin.

From across the gym, Gibbs saw Tony's face. He wore a look of absolute horror.

"Ziva, oh my god, Ziva, I am so sorry, I ... I.." Tony stepped over to her, and raised his hands as if to touch her, and then dropped them again. He was hyperventilating, his eyes wide.

Gibbs moved quickly across the gym, and Ziva began to straighten up as he reached her.

"Ziva, are you okay?" he asked, grasping her shoulders to hold her up. Slowly she stood fully upright, and wiped her hand across her mouth, blood from her lips smearing the back of her hand. Sucking her bottom lip into her mouth to staunch the bleeding, she nodded perfunctorily at Gibbs.

"M'okay," she muttered through a closed mouth, still blinking and shaking her head slightly as if to clear it from the impact.

Gibbs turned his attention to his senior field agent, who stood in front of Ziva, his hands clenching and unclenching at his sides, his shoulders hunched, brow furrowed. But it was the anguish in his eyes that struck to Gibbs' heart. "I'm sorry," he muttered pathetically. "I'm sorry, I'm so sorry Zi."

Ziva looked at him, and then glanced at Gibbs, one eyebrow slightly raised. Tony saw the look, stiffened and fell silent. Dropping his eyes, he turned and walked from the gym.

Gibbs heard him throwing up as soon as he entered the men's room. The noise from the closest stall was gut wrenching. Gibbs leaned against the vanity and said nothing, waiting as the noise subsided, and he heard the sound of the flush. Another minute passed before the lock turned and the door opened.

When Dinozzo first stepped out, he was wiping his hands over his face. Then he straightened up, and pulled at his t-shirt as if to smooth it. Running a hand in a last pass over his face, he tipped his head back and turned it from side to side, stretching his neck. He dropped his shoulders and blew a breath out from between his lips.

It was only when he turned his head that he saw Gibbs standing there, and he visibly started. But he instantly regained his composure. "Hey, Boss," he said calmly, and moved to a basin to wash his hands.

Gibbs shook his head. He was good at this, Dinozzo. It was why he was so good undercover. Not only could he summon up a mask in a second, but it was a damned convincing, almost impenetrable, one.

"Want to tell me what that was about, Dinozzo?" Gibbs asked quietly.

Dinozzo took long moments washing his hands. He scooped a handful of water into his mouth, swished it around and spat it into the basin.

Finally he stood up and spoke. "It was an accident, Boss. Ziva came up behind me. I didn't see her."

"That's not what I'm talking about." Gibbs did not raise his voice.

Now Tony pulled a paper towel from the dispenser, and began drying his hands. Slowly, and with great care, he focused on his fingers, wiping the towel over each one, and then around each wrist.

"It was an accident Boss," he repeated, not meeting Gibbs' eyes. "That's all."

Gibbs stepped closer, deliberately entering Tony's personal space. "That's not what I am talking about Tony," he repeated quietly.

Tony dropped his eyes, and leaned back against the vanity. Gibbs adopted the same pose next to him. He could see Tony's hands shaking slightly as he wadded up the towel and rolled it between them.

"Tony," Gibbs' voice was low, coaxing, almost gentle. "Tony, I'm talking about the way you reacted. What's wrong, son?"

The last word hit him hard, as Gibbs had known it would. He saw Dinozzo close his eyes and drop his head. Gibbs put one hand on his shoulder and squeezed.

Tony gave a slight shake of his head, but he did not pull away. He kept his head bowed, but Gibbs could see his furrowed brow and the tension in his jaw.

"C'mon Tony," Gibbs urged gently. "Talk to me."

Tony lifted his head and tipped it back. Opening his eyes, he stared at the ceiling and gave a heavy sigh. Then he turned his face to Gibbs, and gave him one of those wide, beaming, disconcertingly joyous Dinozzo smiles.

"Any chance of you just dropping this?" he asked, his tone light, almost flirtatious.

Gibbs saw straight through it. Tony's standard defence strategy – a devastating smile and a facetious remark - was not going to work on him. It never had.

"No," Gibbs said softly.

Tony's smile faded, and he looked away. Neither spoke. Tony stopped rolling the ball of paper between his hands, and threw it across the bathroom, unerringly dropping it into the waste receptacle. Then he gripped the hard surface of the vanity behind him as if his life depended on it.

"Want me to help you?" Gibbs prompted quietly. "I expect that whatever you're about to tell me will start with the words "when I was a kid"."

"When I was a kid," Tony repeated glibly, but then he stopped. "When I was a kid...." his voice faded, and he looked down again. He took a deep, shuddering breath, and when he spoke again there was no trace of humour in his voice. "When I was a kid, my... aah, my father..." His voice grew harsh, and his knuckles were white, but he pressed on. "When I was a kid, my father used to ... he used to hit my mother." The words came out in a strangely stilted rush, each word separated from the one before, but choked out as quickly as possible.

Gibbs rested his hand on the back of Tony's neck.

"When I hit Ziva, it made the same sound, and then she was standing there, with blood on her face ..." He closed his eyes, and raised a hand to pinch the bridge of his nose.

Gibbs was silent for a moment, and gently stroked Tony's hair.

"Only your mother?" he asked quietly.

Tony shook his head. "No," he confirmed, almost inaudibly. "Me too, sometimes. More often after my mother died."

Gibbs nodded.

"Boss, I never meant to hit Ziva. I would never hit a woman," Tony said desperately. "I'm not like that. I've never physically hurt any of the women I've gone out with, never. I wouldn't.... I ..."

"I know, I know Tony," he soothed. "It was an accident." He felt Tony nod, and he squeezed his neck. He knew what Tony needed to hear. "You're not like you're father Tony. You're nothing like him. I know that. You need to know it as well."

At Gibbs' words, the tension left Tony's body, and he slumped, leaning slightly to the side. Gibbs welcomed the weight against him, and slid his hand across to Tony's other shoulder, so the young man stood in his loose embrace. For long moments, they simply stood there, resting against each other, one drawing strength, the other happy to provide it. Gibbs felt again the flickering anger at the pain inflicted on Tony as a child, and at the man responsible. It was easy to forget the scars, because Tony hid them so well, but every now and then something would rip them open and Gibbs would see again the depth of the damage that had been done to him. This time, all it had taken was an accident, a sound and a sight, for a long denied childhood memory to tear the heart out of his senior agent.

"Tony, have you ever had to arrest or detain a woman?"

"Yeah," he nodded. "But I've never had to hit one. I don't know if I could."

"You should tell Ziva," Gibbs directed gently. "She needs to know that."

Tony shifted slightly, and Gibbs saw his forehead crease again. "Do you think Ziva... I mean, do I have to tell her the whole..."

"Tell her as much as you want, Tony. But don't underestimate her. She'll understand."

Again Tony nodded. Finally he drew a long breath and stood up, removing himself from Gibbs' embrace.

"Sorry Boss," he said shortly.

Normally Gibbs would have reminded him of the rule against apologising, but not this time. "It's okay Tony." Without analysing it further, he noted that his arm felt strangely empty without the hard warmth of Dinozzo's body beneath it.

Gibbs could see his senior agent regaining his composure, his eyes clearing, and his face adopting into its habitual lines. When Tony pulled back his shoulders and looked him square in the eye, Gibbs spoke.

"Get back to work, Dinozzo," he ordered gruffly.

Tony smiled. "On it, Boss."