Natasha Romanoff woke up from her nightly nightmares, and trudged out to the elevator, and headed up to the common floor of Avengers Tower for some M&Ms. It was the middle of the night, and the only other person ever awake at that time of the night was Steve, so she didn't bother throwing on a robe over her tank top and shorts. After she grabbed a pack of M&Ms from the kitchen area, she went back into the living room and gracelessly plopped down in one of the comfy armchairs to eat her M&Ms and stew in her dark thoughts about the Red Room, the KGB, serving Hydra for years when she thought she was finally going straight, the red in her ledger, and generally how much of a monster she is.

To keep herself busy, without looking she grabbed the closest thing sitting on the table next to her, and began tossing it up and down. She'd been tossing it for a while when Steve walked in, clearly awoken by his own nightmares. As soon as he saw her, though, he stopped dead in his tracks, and stared at her.

Nat looked back at him in confusion, unsure of why he was staring at her. They saw each other in the Tower at all odd hours of the night all the time, since both of them suffered from nightmares nightly, more so than any of the other Avengers. And he'd seen her wearing less on overnight missions back before SHIELD fell, even if he had always turned away as soon as he saw her; hell, he'd seen her wearing less on their frequent nightly encounters in the Tower, to the point where he'd finally stopped looking away whenever he saw her in less than "appropriate" clothing. So she couldn't understand why he'd be staring at her tonight. Then she looked down at what she was holding, and realized what she had been playing with this whole time; Thor's hammer, Mjölnir. The legendary Asgardian hammer that could only be picked up by those who are worthy.

Staring at it in disbelief for a few seconds, she hurriedly sat it back down on the table next to her, and yanked her hand away from it as if it had burned her. Then she hurried out of the room without looking at Steve or saying a word.

Steve never brought it up with her that she'd lifted Thor's hammer, or his suspicion that it bothered her that she was able to. He knew she still considered herself a monster, no matter how many times he tried to convince her otherwise, and certainly wouldn't consider herself worthy of picking up Thor's hammer. Even picking up Thor's hammer knowing the legend couldn't convince her she wasn't a monster.

It was a few weeks later before Mjölnir came back to the forefront of Steve's mind. They had successfully recovered Loki's scepter from HYDRA, and were having a party at the Tower to celebrate it. After all the guests had left, and it was just the Avengers and a few friends, the topic of conversation drifted to Thor's hammer, and Thor's claim that only the worthy could lift it.

Clint was the first to try to lift it, before Tony and Rhodey took their turns, separate and together, and then Bruce took a shot at it, before it was Steve's turn.

He set his feet, and gripped the handle tightly. As he gripped it, he could feel it wobble slightly, but fortunately nobody noticed. So he acted as if he was putting all his energy into lifting it, when in actuality he only gave a tiny amount of effort; he wanted to know if he really could lift it, but even if he could, he didn't want Thor, or any of the others to know. He certainly wasn't interested in ruling Asgard, and it wasn't his weapon to wield in battle.

Even with the small amount of effort he exerted, he could still feel it pull off the table slightly, and could see out of the corner of his eye Thor's expression suddenly turn to one of worry. So he made a show of not being able to lift it before giving up and sitting back down.

As he sat down, he could tell Nat knew what he'd done. And when she was asked to give it a try, he wasn't in the least surprised that she turned it down with an "Oh, no no. That's not a question I need answered"; after all, she already knew she could, even if Steve was the only one to know.

Several months later, after Ultron had finally been defeated, and Cap and Widow and the New Avengers had settled into HQ, Thor had come by for a quick visit. His quest for the Infinity Stones had turned up nothing so far, and he wanted to check in on Vision, one of the few Infinity Stones he knew the location of. And of course he'd brought Mjölnir with him, which he'd left in the common area when he went to bed that night.

Unable to sleep because of their nightmares, Steve and Nat walked into the common area, where Nat immediately headed towards her secret stash of M&Ms (it wasn't exactly secret, everyone knew where it was, but then again who was going to dare steal the assassin's sweets). Not hungry, Steve milled around the living room, when he spotted Thor's hammer sitting on a table next to one of the armchairs. So he strolled over, and casually grabbed it, like he'd seen Thor do so many times before; it came right up.

He tossed it in the air a few times, before looking over at Nat, who was leaning with her back against the bar, watching him, package of M&Ms in one hand, occasionally dumping some in her mouth.

"Catch?" asked Steve, pointing the hammer towards her, and cocking an eyebrow. Nat shrugged her shoulders, so Steve tossed it to her from across the room. She caught it one-handed, tossed it in the air, and threw it back.

They had been playing this casual game of toss for about ten minutes while Nat ate her M&Ms, when Thor walked in, intent on devouring an innocent box of pop-tarts. But as soon as he saw them he froze, pop-tarts long forgotten, unable to believe what he saw in front of him.

Thor had been staring at them for several minutes before Natasha or Steve realized he was there. When Nat finally did see him, she casually tossed Mjölnir to him without saying a word, before strolling over to Steve, brushing her hand lightly across his stomach as she looked up at him, saying, "Ready for bed?", and heading out of the common area towards the living quarters.

Steve looked over at Thor and gave a polite nod and a "Night Thor", before following her out, leaving a stunned Thor behind, wondering how they could be tossing Mjölnir back and forth so effortlessly and what that meant for his claim on the throne of Asgard, and more importantly, when had they started sleeping together?