Trust. It was the lynchpin of their relationship. No matter what situation they found themselves in, Mulder always trusted Scully unconditionally and implicitly. Practically from day one, he could see the strength of her character. Despite knowing she was initially sent as a spy, he could tell almost immediately that her heart was in the right place. In her enchanting blue eyes, he had seen an openness to him and his quest. Her pursuit of the truth was genuine. Over the years, she continually proved her loyalty to the work – and to him – time after time.

All those beliefs about her felt completely shattered when Scully disappeared out of the blue with the Smoking Man. When her landlord told him that she had left with an older man who "smokes like a chimney," he could barely breathe. She had lied to him. Dozens of questions assaulted him all at once. What had she been hiding from him? And for how long? Where did Smoking Man take her? Did she go willingly? If she did, how could she possibly keep that from him?

Finding out about Diana's secret allegiance to the Smoking Man had been bad enough. It had rocked him to his core. For so long, he had trusted Diana and even defended her in the face of damning evidence. All those years of loyalty. What a fool he had been. There was a time in his life when he trusted Diana as much as he did Scully now. Had he been duped a second time? Could he even trust his own feelings anymore? After the disastrous breakup with Diana, he had vowed to himself that he wouldn't fall in love with a colleague again. He had failed at that miserably. Had he foolishly let his guard down only to be hurt and betrayed all over again?

His fears were somewhat assuaged when Scully took him to the Smoking Man's offices. They found them empty, stripped bare of any evidence they had ever existed. Scully had been manipulated by the Smoking Man, just as he had many times before. She had been played like a pawn in one of his sick games. Smoking Man had promised her the cure to all diseases. And Scully, the compassionate person she was, wanted to help others with this groundbreaking science. Smoking Man knew exactly what buttons to push to get Scully to play into his hands. To get her to believe.

Still, this knowledge didn't heal the sting of her lies. The worry he had felt while she was missing had been debilitating, terrifying. If she had told him the truth from the beginning, maybe he could have followed her, watched over her, and discovered the truth about this "Cobra" before she was put in harm's way. She claimed Smoking Man would only grant her this science if Mulder knew nothing of it. Of course. It was a classic tactic of manipulation. Isolate her. Strip her of resources, her support. Mulder refused to believe she couldn't have found a way to communicate with him secretly. In the end, he knew the real reason she didn't tell him. He would have talked her out of it from the beginning. He wouldn't have let her take the risk.

"This was the perfectly executed con, Scully. The only thing I can't figure out is why you're still alive," he said, trying and failing to summon compassion in his voice. This little field trip behind his back could have cost her her life. How could she not see how reckless this was?

"Mulder, I looked into his eyes. I swear what he told me was true."

He almost wanted to laugh. How could she say that? How many times had they been led astray by the Smoking Man? How long until they finally accepted that everything he said was a fucking lie?

"He did it all for himself to get the science on that disk. His sincerity was a mask, Scully. The man's motives never changed," he said, barely able to look at her.

"You think he used me to save himself at the expense of the human race."

"No, he knows what that science is worth, how powerful it is. He'd let nothing stand in his way."

"You may be right . . . but for a moment, I saw something else in him. A longing for something more than power. Maybe for something he could never have."

Mulder looked at the floor and sighed. He didn't want to talk anymore. No matter how she explained it, it didn't hurt any less. Scully was the smartest person he knew, and she let the Smoking Man drag her on an ultimately fruitless wild goose chase. She put her trust in a man who had tried to hinder their work at every turn. And yet, somehow, she was surprised at this outcome. Unbelievable.

She had lied to him. She could have been killed. Those two thoughts overshadowed everything and repeated on an endless loop in his mind.

"Let's get out of here," he said after a long, awkward pause. He wanted to be alone, to retreat.

Scully's face fell, and her arms hung limply at her sides. He sensed her frustration shift inward. She had been tricked, and she should have known better. As much as he wasn't proud of it, he wanted her to feel ashamed of what she did. He wanted her to understand the pain he felt while she was missing.

As they put on their seatbelts in his car, he muttered, "I'll drop you off at home."

"My car is still at your place."

"Right."

He pulled out of the parking spot and pretended to be unbothered. About halfway through the drive, she broke the awkward silence. "When we get back to your apartment, I think we should talk."

"About what?" he replied cooly.

She sighed and pursed her lips. Frankly, he didn't care how annoyed she was at his immature response. He didn't want to talk. Not right now. He needed time to cool down. Since the moment she returned with that damned empty disk, he had tried his best to remain calm. But on the inside, he was experiencing a maelstrom of emotions. He wanted to yell. He wanted to cry. He wanted to shake her. Outwardly, he didn't dare show any of it. He kept his expression neutral, his jaw locked. He shut down, which was ironic considering that Scully was typically predisposed to suppressing her emotions. Usually, Mulder was the one prone to wild outbursts in times of turmoil, while Scully was the master of keeping her composure.

"Mulder," she warned in a no-nonsense voice.

Talking now could only lead to an argument. Part of him wanted to dig in his heels and refuse. But if Scully wanted to hear how he really felt, if she wanted all that was brewing inside him to come out, then . . .

"Fine," he acquiesced.

The rest of the car ride was deadly silent. While Mulder didn't know the full extent of her trip with the Smoking Man, his brain started to fill in the gaps against his will. He imagined them driving together on their little road trip. What did they talk about? What did she share with him? What information did she divulge that Smoking Man could weaponize later? Did they stay at a hotel? In the same room? In what ways did they conspire to keep Mulder in the dark? The thoughts made him sick to his stomach.

By the time they reached his apartment, Mulder was swallowed up by his dark ruminations. He was practically primed for an argument. He threw his keys on the coffee table and collapsed onto the couch while Scully watched awkwardly from the doorframe. He shrugged off his leather jacket and tossed it over the arm of the couch.

"You wanted to talk," he said curtly, "so talk."

Scully hesitated as if unsure where to begin. "Mulder, I know you're angry –"

"Of course I'm angry," he spat. "You lied to me. You hid things from me. You ran off with him behind my back!"

Scully crossed her arms defensively. Measured and deliberate, she started, "He offered me a cure for –"

"He set you up! And you fell for it." He laughed ruefully. "How could you be so –"

Her eyebrow arched, daring him to finish the sentence.

"You're right," she said. "I was misled."

He shook his head, furious at how calm she was. He felt like a bomb ready to detonate while she stood there like a statue. One wrong move, and he would explode.

Putting his head in his hands, he said, "Can you please just leave? We'll talk about this later."

"Please give me a minute to hear me out. And then I'll leave."

Her expression softened when he looked up at her, her eyes pleading. With reluctance, he gestured for her to go on. She took a few steps toward where he sat, her heels clicking on the hardwood.

"I want you to think back to when I had cancer," she began.

"Scully, come on –"

"Please, just listen. Think back to that time. Think about everything you did to try to help me. To find a cure for me."

The words hit hard, as intended. Her illness had been one of the worst times in his life. He would have done anything – traded anything – for her recovery. He didn't want to hear this. He didn't even want to think about it. And he really didn't want to hear anything that would make him feel unjust in his anger. He wasn't ready to let go of his righteous indignation.

She continued, "He claimed to have cured me. And with the science he offered me, he said I could cure others. Imagine how many lives we could save."

So fucking selfless. Of course. This is exactly why he didn't want to talk about this yet. Even her altruism irritated him.

Abruptly, he stood from the couch and crossed the room, putting space between them. "I couldn't get to you!" he blurted out. "I didn't know how to find you! You could have been killed. What don't you understand?"

Scully's mood shifted, and he saw his anger reflected in her eyes. "I do understand, Mulder," she said, her voice taking on a more aggressive edge. She advanced toward him, uncrossing her arms. "How many times have you run off without so much as a word in my direction? How many times over the years have I laid awake in bed at night worrying about you chasing down some mysterious lead? I'll tell you – more times than I can count."

A fire ignited in her eyes, and he liked it. He liked that she was engaging in the argument, matching his energy. He wanted to shove her against a wall and kiss her until her lips bruised. And that's when he realized why this hurt so badly. Since their first kiss, their relationship had been progressing – albeit slowly – into something different. It was more than partners. More than friends. They had become much closer and more vulnerable with each other over these months. He had agreed to have a child with her, for Christ's sake.

"It's different now!" He hadn't intended to say it, but the words fell out. Softer, he added, "Things are different now."

This disarmed Scully. She seemed shocked by this outburst. Her breathing became quicker.

"What does that mean?" she asked.

"It means . . ." he trailed off, struggling to articulate his thoughts.

It means I love you, he wanted to say. He wanted to yell it. I love you, and if anything happened to you, I would die.

"It means," he tried again, choosing his words carefully, "that we're not just . . . partners anymore."

Scully sucked in a breath. Her eyes pinned him with a look that said she was anticipating something more.

After a long pause, she finally said, "And what are we?"

His heartbeat sped up. He had pondered that question often since they kissed for the first time. Unfortunately, he didn't know the answer. They were still partners. Still friends. But they had kissed on multiple occasions; they were attracted to each other.

On his side, it was simple. She was the love of his life. He loved her more than he had ever loved another person. Period. He couldn't imagine another woman in his life besides Scully. Maybe ever. She was it. If soulmates were real, she was his. He wanted her in every conceivable way.

He knew she cared about him, yes. Maybe she even loved him. But was she in love with him? Did she love him, want him, with the same ferocity? Did she truly want to be with him?

Diana's words rang in his ears: You can't give her what she wants, Fox. I know you. And settling down – marriage, kids, playing house – it's not you. Do you really think she's going to follow you on your crusade forever? Don't you think she deserves better?

As much as he hated to admit it, Diana had been right. Scully deserved all those things she wanted. What if he was simply not built for domestic life? Would a romantic relationship with Scully be doomed to fail? Would he disappoint her? Was it inevitable that he could never make her happy? Even if they tried to be in a relationship, how long until she got sick of waiting for him to settle into a normal life?

The IVF attempt with Scully did make him question whether he could want a different life. A quieter life. For the first time, he seriously considered a different path. And since he found out the truth about Samantha's death, the work had felt less pressing. Less heavy. Less all-consuming. Things were changing. However, there will always be more to find, more to uncover, more secrets to expose. This trip with the Smoking Man proved it.

Scully's expression was inscrutable. She wanted an answer; she begged for it with her eyes. But he couldn't tell what she wanted that answer to be. One wrong word could unravel things between them forever.

"What are we?" she repeated, softer, as if now she was asking herself.

More than anything, he wished they could have this conversation but in an entirely different context. He didn't want to have it now when the sting of her betrayal still loomed over him. A dull ache lingered in his chest that only intensified as he gazed into her eyes. No matter what he said next, it wouldn't suffice.

"I don't know," he finally said, the words paining him to say. He forced them out with effort. "I don't know, Scully." It was both the truth and a lie at the same time.

Her face grew tight, and she nodded. He had disappointed her, just as he knew he would. What he said was the wrong answer, yet he still had no idea what she wanted him to say.

As he often did in tense moments, he wanted to make a joke. Rain check this conversation? he could say. But he wouldn't. He didn't want to sully the fond memories of the other times they had used that phrase. Nor did he want her to think he wasn't taking this moment seriously.

"I don't think this is a good time for this conversation," he said, trying to appeal to her rationality. "I need to cool off. I'm sorry."

Her arms fell to her sides as if to say I give up.

This time, he could tell what she was thinking without her having to verbalize it. When will it be a good time for this conversation? When has there ever been a good time for this conversation?

"I understand," she said tersely, her eyes beginning to water. "I'm going home."

In seconds, she was out the door. He almost ran after her. After all, his hallway seemed to be the place where he always bore his soul to her. His feet felt glued to the floor. He let her go.