Recently:

Catherine was just walking from the Palace across the parking lot to the car when, surprisingly, an old acquaintance stood in front of her.
"Hey, what are you doing here? What brings you to Hawaii?""I'm done."

"How? You mean really done?

"Yes, soon the uniform will go into the closet and I won't get any more money from the government."

"Wow, so what's the next chapter in the life of Billy Harrington?"

"Well, maybe I'll tell you that over dinner."

"Billy, I have a boyfriend."

Clearly disappointed, Billy took a deep breath and then voiced his suspicion, trying not to let his disappointment and jealousy show.
"McGarrett, right?"

"Yes."

"In Amsterdam you told me it was over with you two."

"It was at the time and it was something serious between the two of us and I will never regret Amsterdam or our time in Kabul. But that was five years ago, Billy, and things are changing."

"Well, just in case I'm staying at the Ilikai Hotel."

Catherine didn't respond to that statement, just pulled Billy into a hug.
"It was nice to see you."

"I was happy too."

Billy turned and went on his way. Catherine watched him go. She knew for a fact that she loved Steve and not Billy, but some memories of her time with Billy were just flooding up. It had really been a good time and she really didn't regret it, he had been incredibly loving and caring back then, just like Steve was to her.

"Catherine, who was that?"

Steve was now standing behind Catherine, who immediately turned and looked at him.

"That was Billy Harrington. You should remember him, you served together."

"Of course I remember him. He was your ex-boyfriend too."

"Yes, but you know it's over."

Steve looked amused as he enjoyed teasing his girlfriend a bit about it.
"Sure. What did he want?

"He just told me he is out of the Navy."

"Well then. So, do you want me to drive you home or are you coming with me?"

"Well, whatever the Commander prefers."

Catherine stepped even closer to Steve and looked into his eyes.
"If you say so, Lieutenant. Then I guess I'd rather take you with me."

The two kissed briefly and got into the Silverado.

On the drive, Catherine suddenly remembered something.
"What did you actually want to ask me this morning, just before the blackout?"

"When you told me about your nightmares, I assured you that you are not alone, that I am with you. And then I was wondering if you...well, maybe you'd want to move in with me."

There was a brief silence, because Catherine hadn't expected this question.
"Yes, I would love to. In fact, I already spend more time in your house than I do in mine."

That was the answer Steve was hoping for. He was very happy, which also pushed aside the fact that Billy was back on the island.

The next day, the team met at HQ to complete yesterday's paperwork. At least no new case was coming in, so they could work undisturbed.
However, around 5 p.m., Billy suddenly came into HQ and purposefully headed for Steve and Catherine's office. Steve was in Danny's office right now, so all he saw was Billy walking over to Catherine and talking to her. But since Steve had served with Billy, he trusted him and didn't think Billy would come between him and Catherine.

Catherine was surprised when Billy suddenly came into the office and was curious what he wanted from her.
"Hey, Billy, what are you doing here?"

"I wanted to talk to you again and thought I'd rather do that in person."

"Okay, what can I do for you?"

"I'd like to invite you to dinner. And before you say anything, I know you're happy with Steve and I accept that. Believe me, I would never come between you two. But we haven't seen each other for years so I'd love to have dinner with you, just amicably, to catch up on the last few years, you know."

Catherine thought for a moment, but then made her decision. Nothing could really go wrong.
"Okay, I accept your invitation."

"I'm pleased. Then let's go."

"What, you mean right now?"

"Yes, is that a problem?"

"Um, no, let me just give Steve a quick word."

Catherine got up, walked past Billy, out the door, and into Danny's office. "Steve?"
Steve turned his gaze to the door and looked anxiously at Catherine.

"Billy asked me to go out to dinner with him, only on a friendly basis as we haven't seen each other in years. Do you, well, have a problem with that?"
Steve was a little amused that Catherine asked his permission like a little girl would ask her parents.

"Of course I have no problem with that."

Catherine looked at him for a moment, reading his expression.
"Oh, come on, you're lying."

"Maybe a little... Listen, I trust you, okay? That's enough."

Steve got up and saw that Billy was waiting in the hallway. Actually, he just wanted to hug Catherine and wish her a nice evening, but when Billy was already watching, he couldn't help it and entangled Catherine in a long kiss.

"See you later and have a nice evening."

"Thanks and you, don't work so much, okay?"

"Got it."

Catherine walked out of the office to Billy who smiled at her and they both left the HQ.
Steve sat back down on the sofa in Danny's office and looked at Danny.

"Steven, would you please explain to me what the hell you just did?"

"What am I supposed to have done? It's hard for me to tell Catherine who to meet with."

"You just told your girlfriend that it's okay for her to go out to dinner with her ex! That's just stupid!"

"Danny, I served with Billy. He's absolutely decent."

"That's why it was a terrible decision!"

"This is nonsense!"

"Think about it. Now if the two of them meet, this Billy is going to stick around and see Catherine more often and eventually the two of them will have that one moment."

"One moment?"

"A moment when they look at each other and suddenly everything is like it used to be, the old feelings are back. And the only one to blame is you! Because you let her date her ex."

"Are you done with your silly assumptions, or is there more to come?"

"You can deny it as long as you want, but that won't help you. Trust me, I'm your friend, I know that."

Steve didn't want to admit it, but somehow Danny was right. He did trust Catherine and he did trust Billy, but he hadn't seen him in four years and people change.

To take his mind off things, Steve went back to his office and continued working.

However, after about three hours, a Palace security guard walked in and handed Steve a brown envelope with his name on it.
"Commander, this envelope was just found in the mailbox. It has already been scanned, there is nothing dangerous in it."
"Okay thanks."
The security guard left and Steve put the envelope on his desk and sat back down...

Hope you liked it :)