So I've been watching some of the old NCIS's and this popped into my head.
It's set somewhere in season four, after Gibbs comes back, and ignores any relationships that Gibbs and Kate were actually in on the show, like the red head in the car and Tony's frat brother.

Ziva was feed up with her desk drawer sticking so when she had a free moment between filing and cases she decided to sort it out.

She pushed her chair back and put her keyboard out of the way. She then pulled out the sticking drawer the whole way, putting it on the desk in front of her. She first checked the runners, making sure they weren't gummed up or anything. When she saw that they were clean she made to look at the drawer itself but was stopped by Tony asking.

"What are you doing Ziiiiiva?"

"The drawer sticks, I am finding out why."

Tony nodded then got up and walked over and sat on the edge of her desk. Ziva glared at him, "Do you not have anything better to do?"

Tony shook his head, "Nope."

Ziva sighed but started back on the drawer. She ran her hand over the edges, feeling if there were any bumps or lumps in the drawer that would impede the movement of the drawer . Finding nothing she ran he hand over the back, seeing if there was anything sticky. Finding nothing yet again she sighed.

"Didn't find anything?" Tony asked.

"Clearly," Ziva sighed.

Tony titled his head to the side then asked, "What about the bottom? Maybe there's something that's catching on the drawer below."

Ziva nodded and slowly began putting the contents of the drawer on her chair, since Tony was sitting on the only bit of desk not taken up by the computer, phone or drawer. Once the drawer was empty she flipped it then froze when she saw what was stuck to the bottom. "Looks like you were right Tony, there's something on the bottom." As she spoke she peeled off the tape and took the envelope addressed to Gibbs off the drawer and handed it to Tony giving him a warning as she did, "Don't open it Tony, it's not addressed to you." She righted the drawer and began to re pack it.

Tony nodded but it didn't stop him shaking it and squeezing the envelope. Or at least he did until it was snatched out of his hands and he got a head slap added in. "It's not addressed to you DiNozzo and you know what happened last time you opened someone else mail," Gibbs said, walking over and sitting behind his desk, the envelope still clutched in his hand.

"Yes boss, but in all fairness, it was addressed to NCIS Special Agent," Tony pointed out. Gibbs gave him a look and Tony carried on to say, "But never mind that now."

By now Ziva had repacked her drawer and slid it back into place. She looked over at Gibbs, "What is it Gibbs?"

"It's a letter," Gibbs answered, turning the envelope over and over in his hands.

"Who from?" Ziva questioned, watching his hands.

"Kate," Tony answered, "I'd recognise the hand writing anywhere." Gibbs nodded. "Are you going to open it boss?" Gibbs gave him another look, "I'll just shut up now."

Ziva smiled while Gibbs turned his attention back to the letter in his hands. He pulled out his knife and slit the top. After putting his knife away he pulled out the letter inside. He read it silently for a few minutes then pulled something small out the envelope and left, without saying a word.

Tony and Ziva's eyes both followed his path but when he got out of sight they both stood and made their way to Gibbs' desk and Tony picked up the letter that Gibbs had left on the desk. McGee not far behind, although thus far he had decided to stay out the way, but as soon as he found out it was a letter from Kate he couldn't help but wonder what it said.

May 24th 2005

Jethro,

If you're reading this I'm dead and whoever got my desk got tired of the drawer sticking.

I wanted you to know that I have loved working at NCIS and I'm so glad that you offered me a job after I left the secret service.

Since I'm dead and probably buried by now I can safely tell you to tell Tony that even though he's a complete pig most of the time I'd like to think of him as the annoying brother I never had and hadn't realised I wanted until I meet him. Tell McGee he was like my brother too, just nowhere near as annoying. Tell him not to let Tony's jokes and pranks to get him down. Keep them safe Jethro, they make one hell of a team and you need them just as much as they need you. Tell Abby that I love her like the second sister she became, and I hope that she doesn't mourn too long, life without a happy Abby is not life at all. She has to keep happy and strong so everyone else knows that it's not the end of the world.

Tell whoever my replacement is that it gets better. Tony eventually grows on you and that they will even get used to the functional mute that is you Jethro.

Ducky, tell him I'm thankful to him for keeping me covered when you came and said goodbye. I know he will, he's one of the best people I know. Please tell him I love his stories and that he should never, ever, stop telling them.

Now you Jethro, there's only one thing I want to tell you, the answers yes of course I will. I would tell you in person but we're on protection detail and I can feel in my gut that I may not survive it. Ari is a bastard and you know he's going to go after the people you care about in your life, especially after what happened to Shannon and Kelly. I know I said it at the time but I'm sorry it happened Gibbs; they were doing the right thing and got killed for their trouble.

I've already said that I don't think I'll survive this protection detail but if I do I'll burn this letter and give you my answer in person.

I know you said you were too old for me but that doesn't change the fact I love you Leroy Jethro Gibbs, every single grey hair and bad memory included. I'm sorry that I've gone and left you but I do love you and I would love to be your wife, of course I'll marry you. The ring is in the envelope and I'll wear it as soon as this case is over and done with, and if I die you can have it back and get on with your life.

I love you Gibbs, now and forever

Kate x

P.S. There are some pictures I drew in the envelope and I hope it gives you and the rest of the team something to smile at when things get bad.

Tony looked up from the letter and caught McGee's eye. "He proposed?" Tony mumbled to himself.

McGee nodded, "I didn't even realise they were together."

"That's because we kept it quiet McGee," Gibb's voice said from behind them. They all turned, looking sheepish, but Tony most of all. "Yes I proposed, a few days before Ari came back. She wanted to think about it so I gave her the ring and left her to it."

Ziva found her voice first, "How long were you together Gibbs?"

"Nearly two years. We started dating just after the submarine case."

"So she was going to be wife number five then boss?" Tony questioned. Gibbs slapped him across the back of the head, "Sorry boss."

Gibbs nodded then spoke, "Yes Tony, she was going to be wife number five, and she was going to be the final one." He picked up the envelope again and pulled out the picture Kate had said was in there.

He unfolded it and smiled. There were two. One was a group of cartoons of everyone. Abby was a bat, McGee was on a computer, Tony was watching some women's ass, the same as the larger one she had done in her sketch book just smaller. Ducky's was good, he had a scalpel in one hand and a speech bubble above his head full of squiggly lines. When he got to his cartoon Gibbs smiled, he had his weapon out and up and was firing. Gibbs handed the paper to Tony and McGee and looked at the next one. It was a drawing of the whole team. Gibbs was in the middle with Abby on one side and Kate on the other. Ducky was standing next to Abby and McGee was next to him while Tony was stood beside Kate. All of them were laughing and smiling and looked incredibly happy. As Gibbs studied it reminded him of something and when he got it he smiled. It was similar to the photo someone had taken at the Christmas party the year Kate had joined them, just without the decorations.

He smiled lightly and handed it to Tony and McGee. The two agents smiled and Ziva smiled, "She was an amazing artist Gibbs."

Gibbs nodded, "She was."

"I can't believe she saw me as a brother," McGee said, while Tony nodded beside him.

"We are all a family," Ziva said.

They all nodded and Gibbs held out his hand for the pictures. Tony and McGee handed them to him and he stood once more. He moved to one of the plasma's and stuck the two pictures to the top of the monitor. He stepped back and smiled sadly, "I love you Kate, and I miss you every day."