Kate went into the bathroom first, then it was Castle's turn. Finally Colin disappeared in the en-suite, and as soon as the door fell into the lock behind him, Kate turned to Castle.

"Rick, if you want to stop, all you have to do is say the word." She prompted him. "I don't want to force you into anything."

Castle gave a laugh, "A little bit late for that now, is it? But thanks for the offer." Kate rolled her eyes. Castle crossed the floor to take her in his arms and looked at her seriously. "Kate, I love you and this is by far the hottest experience of my life. The hell I want to stop now."

"I love you, too," she replied and they kissed passionately.

They didn't interrupt their kiss, when Colin returned form the bath. It didn't really bother the Brit anyway, this way he could observe them in quiet. Colin liked being with attractive, sexually open-minded people, which included both Kate and Castle for him. He let his gaze wander over Castle's broad back, his muscled arms, and his firm butt. Just the look of the couple kissing passionately in front of him was enough to harden his cock.

"Nice of you two starting without me," Colin smirked. "Now what's next?"

Castle and Kate tore themselves away from their kiss and looked at Colin who stood in front of them with an erection and full of expectations. Castle had to admit that Colin was anything but unattractively.

Kate turned red at the thought of what she was going to ask of both men any moment now. "I want you both… in me… at the same time," she began hesitantly, "I want to feel both your cocks inside me."

Colin had kind of already anticipated that and was ready for everything. Castle, on the contrary, looked at her surprised at first, but gathered his bearings again quickly.

"Okay," he directed his next question at Kate, "Who, where, and how?

Kate hadn't gotten that far in her thoughts, this was her first time even voicing that desire. All she knew was that she wanted to be as close to Castle as possible.

"Get on your back," she instructed Castle after a moment's thought. He immediately followed her request. Kate crawled to him on the bed and straddled his thighs. She grabbed his hard cock and gave it a couple of strokes, before she positioned herself above him and sank slowly down onto his cock.

Castle pulled her down and kissed her gently. He let his tongue trail across her lips until she opened them and he could delve deeper into the cavity of her mouth. Kate moaned into his mouth, as he lifted his hips and thrust into her carefully.

Colin savored the sight of the two lovers in front of him, however, he wanted to participate in the games as well. Therefore he cleared his throat to draw Kate's and Castle's attention back to him.

"Where do you keep the lubricant?" He asked Kate when she looked up to him.

"Top drawer," she replied, pointing to the night stand.

Colin retrieved the gel and moved to the end of the bed. He tapped Castle lightly on the shin, so the other man would make space for him. Castle spread his legs apart and Colin knelt in between them. He put his hand on Kate's ass and stroked her cheeks softly. She tensed with excitement, he could see, and then she stopped moving on Castle all together.

"Relax," Colin smirked and kept stroking her lower backside and butt. Castle began stroking her back as well, but stayed near her shoulders, so he wouldn't hinder Colin.

Kate searched for Castle's eyes, reassuring herself that he would not hold a grudge against her over this. When she found his eyes, he gave her an encouraging and loving nod.

Only when Colin could feel Kate's muscles relax, did he squeeze some of the gel between her ass cheeks. The cold startled Kate. But she didn't have time to think about it, because Colin spread the gel quickly and pushed his finger into her anus.

Oh, that felt nice. Kate moaned into Castle's mouth. Her boyfriend and Colin began to move slowly inside her, too slowly. She needed more. She pushed herself alternatively between Castle and Colin to increase the friction. After a few thrusts, Colin added another finger, spreading her.

"Colin, please," Kate begged him, when the tension became too much. She wanted both of their cocks inside her already.

Colin removed his fingers and Kate felt more cold gel and then the tip of his cock against her anus. She tried to relax and was grateful that Castle had stopped moving. This way she could fully concentrate on taking Colin inside her.

She pressed her torso deeper into Castle, resting her head on his shoulder. At the same time she pushed out her butt a little further, carefully to keep Castle from slipping out.

Kate didn't know whether Castle and Colin were using any signals, but suddenly both started moving inside her simultaneously. Castle thrust deeply into her from below, while Colin rocked slowly into her, entering her a little bit more with ever forward motion.

Kate thought she would burst, it was too much and yet not enough. She wanted to come, but then again not really, because it felt so good, this feeling of being completely filled. She wanted to savor it as long as she could. For now she was still in command of her body, but the men moved faster, harder and wilder inside her.

"Come for us, Kate!" Castle encouraged her, as he shoved his fingers between their bodies and rubbed her clit. "I'll catch you."

And then it was time, Kate couldn't stop it any longer. She cried out, alternating both men's names, while her orgasm wrecked her body. She felt as if she'd been flying. And it wouldn't stop because not only Colin but Castle also kept thrusting into her relentlessly.

Just when Kate began to fear that pain might overtake her elated bliss, she felt Castle stopped moving and released inside her. She tensed her vagina's muscles with her last bits of strength, milking every last drop of semen out of him. Her inner contractions also triggered Colin's climax, who emptied his balls for the second time inside her body.

Completely drained and sated, Kate collapsed on top of Castle, bringing Colin down with her, who fell panting on the mattress next to them. Castle rolled away from underneath Kate, so she ended up sandwiched on the bed between him and Colin.

Kate lay on her belly and turned her head to Colin. "Thank you," she exhaled breathlessly, and brushed his cheek.

Colin kissed her softly on the mouth, "Anytime."

Turning onto her other side, Kate sought out her boyfriend, who immediately pulled her close.

"I love you," they said simultaneously and laughed about it freely. Then Kate snuggled into him and was asleep within seconds.

When Kate woke up again, it was already light outside. She was still lying in Castle's arms. Her boyfriend was snoring softly. Kate withdrew from him because the damp spot she was somehow resting on bothered her. The memories of last night returned and Kate turned around for Colin. But he was gone. She sat up and realized his clothes were no longer on her bedroom floor either. Colin must have slipped out sometime in the dead of the night. Kate sighed because he was a good friend and she found it sad that he hadn't said good-bye. Especially because she wasn't sure if she'd ever see him again.

Castle stirred next to her and rose from his sleep. "Hey," he greeted her, sleep still dazzling his eyes. "Are you ok?"

"Yeah," she smiled in reply, "just a little sore in some places."

"Oh yeah, I can only imagine." Castle grinned and straightened up. "Where's Colin?"

"Gone apparently." Kate shrugged her shoulders. "What did you talk to him about before you came to my bedroom yesterday?"

"Just making sure that we were all on the same page and Colin understood what this was really about." Castle explained.

"Oh and what has all this been about according to you?" She asked unsure.

"You, of course," he replied seriously. "Just you. I made it clear that this was solely about your gratification, not his nor mine either. But turns out he saw it the same way, so we reached a consensus very quickly."

"Then what were the two of you chatting about for so long?" She asked now curiously.

"Wouldn't you like to know?" He retorted laughing and Kate rolled her eyes. "Can't two men enjoy exchanging notes every once in a while? I learned a lot about you… and I kinda like Colin."

When Kate and Castle came into the kitchen for breakfast after a mutual shower, they found a note on the counter, saying:

Thank you!
I had a lot of fun with you both.
Next time, I want to try something out.
Castle, get ready.

Until then,
Colin

Castle stared at Kate in shock and a little frightened, but his girlfriend just laughed and patted his hand. "Don't worry, Colin's really good at it. You'll like him even more afterwards."

The End

A/N: Thanks for reading and the feedback. Constructive criticism is always helpful.
However, no one was forced to read this story. Those who have complained are welcome to do better.