Wow, guys! Sorry I'm so late this week! My work schedule was crazy the last few days, so I didn't get a chance to update. Anyway, you all have been asking, and I've been passive-aggressively refusing to answer . . . but explanations are happening! That's right! Some of your questions will be answered in this chapter! Your patience is being rewarded. :-) Hopefully, this is as helpful for you as it is to the Avengers (who really don't know any more of what's up than you do). Enjoy, and I'll try to be more timely next week!

*Also, note: Part of this chapter takes place on Asgard. It is not in italics. No, I didn't forget or anything; the italics always meant that the events occurred in the past, relative to what's happening in the non-italics. Now, past and present are caught up, and both are happening simultaneously. Just to avoid confusion.

Tony had spent the better part of the morning searching the tower up and down for them. More specifically, for her. Clint and Natasha could vanish without a trace and Tony wouldn't question them, but she, however . . . he somehow felt responsible for her, and the fact that he couldn't find her was unsettling to say the least.

"Nothing on floors one through twelve," Pepper reported as she stepped off of the elevator.

Tony cursed. "Where else would she go?" The question was rhetorical, but the hope that Pepper might be able to reply still niggled at the back of his mind like an itch that he couldn't scratch. He ran a hand through his hair absently, already thinking of places they hadn't yet looked that might be worth checking.

"She'll be alright," Pepper told him, though her voice lacked enough confidence to adequately reassure, instead having the opposite effect. Pepper noticed, and was about to say something when the elevator dinged open.

In a flurry of black neoprene punctuated by Natasha's red hair, all three missing parties spilled from the box, adventure written all over them.

Before Tony could decide whether to ask them seriously about where they've been or give them grief for (almost) scaring him half to death, Elizabeth caught his shoulder while the two assassins filtered past. "Stark, I need you to assemble your Avengers immediately," she said. "It's urgent."

The look in her eyes told him that he had little choice but to nod and take Pepper off to go grab the others. At least he knew they were in the tower.

Ten minutes later, every relatively permanent occupant of Stark Tower sat in the living room, tossing around furtive glances as Elizabeth paced in front of them, hands clasped behind her back, expression unreadable.

"I trust you remember the Chitauri," she began, not breaking stride. "They comprised Loki's army when last you encountered them."

"Those weird robot hybrid things?" Clint asked.

She nodded gravely. "The very same. I fear that you didn't get the opportunity to see them in the same light as the rest of the universe. For, you must understand, they are fierce warriors with a heady capacity for vengeance and a bloodlust to rival any in all Yggdrasil. Though they are essentially an army for hire, they are not to be trifled with." She paused, surveying them for any sign of extreme confusion. When she only found moderate disbelief, she continued.

"To have the Chitauri on your side in battle is to very nearly guarantee victory. As such is the case, they are unused to losing." With a quick glance at the faces surrounding her, she added, "Especially not to a ragtag band of mortals, if you'll pardon my saying so."

Tony scoffed. "Well, I for one would be more than happy to beat them again," he said. "Maybe then they'll get used to it."

"The Chitauri will never grow accustomed to defeat," Thor returned, shaking his head. "They take sides based upon the potential benefits to be reaped upon winning. That sort of mentality will never take kindly to loss." He looked up at Elizabeth for confirmation, and she nodded once.

"Indeed."

"So why does it matter?" Tony asked. "We fought. We won. Go team."

Elizabeth shot him a glance so incendiary that it could have lit a candle. "It matters because, despite what you may think, you lack vital information." Then, turning back to the group as a whole, she said, "Some Chitauri, if they show promise in the wielding of Seidr – that is to say, magic – are endowed with the coveted ability to change their form at will. You call it shape-shifting. So long as they have laid eyes on their target enough to memorize his, her, or its appearance with accuracy, these Chitauri will be able to assume the countenance in question. The best plagiarists, however, are those who know their models so intimately that they can not only imitate a face but the finer details as well. A manner of speaking. Posture. The ability to wink, and with which eye to do it."

"Correct me if I'm wrong," Bruce said, "but you're saying that we could have one of these . . . shape-shifters hanging around right now?" When she didn't say anything in response, Bruce added, "We'd have noticed, right?"

Elizabeth merely twitched an eyebrow. "This is their purpose in life, and they are very good at it. There are whole divisions – fleets – of Chitauri Scrimori, mimics who have been granted ease with this practice to allow them to slip undetected behind enemy lines. You can imagine the advantages of such abilities, of course. It is their greatest asset and their greatest secret. Few can recognize a Chitauri Scrimorus when it is in its disguise, making them some of the most efficient spies known."

Everyone sat silently, a salty tension resting over them as they all realized the implications of what she was saying. Steve cleared his throat and voiced what everyone else was thinking. "But, if the Chitauri have such a drastic advantage, how did we ever win?"

"You almost didn't." Elizabeth stopped pacing abruptly in favor of standing stiffly – darkly – before them. "Besides, there were no Scrimori in that army; don't flatter yourselves. Sometimes, though – only with extreme rarity – a Scrimorus will slip." She picked up the remote and flicked on the television, the screen still steeped in the frozen image of Loki. "For example," she stated plainly, gesturing toward the screen.

"Meet your first Scrimorus," she said with the professional air of Nick Fury during a debriefing.

Thor leaned toward the screen. "It is a remarkable likeness," he muttered, scrutinizing it in a way entirely unique to him. "I cannot find a fault in it, and I have known Loki my entire life."

"It is remarkable, yes," Elizabeth allowed. "It had all of you fooled."

"You kept saying it's impossible for Loki to be here," Natasha breathed.

"And so it is."

"Pray, where is its mistake?" Thor asked. "Even I can find nothing."

Elizabeth strode toward the television, a touch too much swagger in her steps. Still, she remained entirely somber as she too stared at the screen. "I didn't realize it was a Chitauri Scrimorus; I only ever knew that it was not the true Loki," she said.

"But what tipped you off?" Clint asked, echoing Thor and Natasha.

For a moment, Elizabeth was quiet. Then, she replied, "It chose the wrong audience." She raised her eyes to meet the questioning gazes of the others, continuing, "It had me concerned enough to desire a word, and, when I spoke with it, the impersonation was obvious."

Thor's bright eyes had narrowed on her, fixing her with the closest thing to shrewdness in his facial vocabulary. "And you know Loki well enough to tell?"

She straightened, lifting her chin a fraction of an inch in defiance. "Had you been there, I assure you that you would have perceived the fake as well. One only needs to know the right questions to ask."

"Personal questions," Clint clarified, recalling her comment from the cab ride.

The corner of her mouth slid upward into a slight smirk, and she winked. The gesture was devoid of any sort of humor or light-heartedness, but it served well enough as a response. To everyone else, she said, "I prefer to think of it as basic Loki trivia. To Loki, the answers to my questions would have been rote – if a touch uncomfortable. Yet this Scrimorus knew not one of them. I merely tested it, and it failed."

"So, what now?" Steve asked, glancing around at his compatriots to find the question in their faces as well.

"Now," Elizabeth said, drawing a deep breath, "we kill it. Before it kills us."

The training grounds held no appeal to her today. Since after breakfast, she had been out in the dusty ring, trying to muster the motivation to put herself through her paces. It was insufferably hot – the type of day on which it would not have been uncommon to find Thor lying on the brink of sleep in the middle of the dirt, Loki clinging to the shade under the nearest tree as if the shadow held the key to his life. In hindsight, Sif reasoned, the difference between them made significantly more sense when Loki's true heritage was taken into account. It explained nearly all of his peculiarities, actually.

But, given that neither prince was present that afternoon – the whereabouts of only was known to her – she was left with little option but to do as she had always done and fight the heat like an enemy, training simply to spite it.

In all her hours in the ring, though, she had perhaps spent only one of them engaged in proper training. The rest had been whiled away between frustrated sighs and bouts of pacing, the tip of her sword carving a thin divot in the ground as she traipsed back and forth aimlessly, as though idle movement could do something to ease her discomfort.

The sun blazed mercilessly down at her, reflecting off of her armor and blade with force enough to blind. It sweltered, and she felt like a pig roasting on a spit over an open flame. She certainly sweated like one.

There had been countless hot days in the centuries of her life, but this one put them all to shame. Had Loki been around, they probably would have slipped off into the woods for a swim in one of the secret ponds they frequented when they could be certain they wouldn't be missed. Unbidden, her memory slunk back to dredge up the image of his hair, long, dark, and soaking wet, reflecting the light like a black mirror – a bottomless pool with a glassy surface.

She sucked in a breath through her teeth and reminded herself that her own hair probably looked exactly the same when she surfaced after a dive; somewhere inside her, though, she knew hers could never be so brilliant.

Lifting her sword in an effort to give her mind something more productive to do, she attempted to run a full attack pattern. She stopped when she realized that she had unconsciously been tailoring her maneuvers to Loki's height, as if fighting a macabre ghost of him.

Annoyed, she threw down her sword and stalked over to sit on the grassy slope beside the ring.

She imagined – imagined, or remembered? – exchanging a longsuffering glance with the youngest prince while the oldest snored away quite contentedly in the full flare of the sun. At this, she almost made to get up again, retrieve her sword, and slash through more formations, but she immediately gave this up. Her heart clearly wasn't in fighting today. Instead, she ran her fingers through the grass, letting the soft blades tickle her. She breathed in, breathed out, and let the memories of stifling days-gone-by surge.

A wry smile.

The singular way that sweat glistened on his skin, looking as unnatural as the sword by his side.

His pained looks at Thor, as if he couldn't understand how anyone could sound so much like a dying troll while sleeping.

The vividness of the image itself didn't surprise her, though her sudden recollection of minute details did: the neck of his shirt always laced tighter than anybody else's, though never truly tied; the heaviness of his breath, as if the heat alone exhausted him . . .

She shook her hair back, face upturned so that the ends of it trailed in the grass. It amazed her how difficult a hot day could be when she didn't have the two princes and the almost-comical dichotomy between them keeping her mind from such trivial things as weather.

"Sif!"

At the sound of her own name, she lifted her head blearily and turned toward the sound. Fandral was running toward her, though only at half his normal speed and with heavy, slogging steps. He stopped a few yards from her, panting. "It's too hot for this," he moaned.

She would have nodded in agreement, but the sauna around her had rendered her incapable of such a movement for the time being. Instead, she said, "What is it, Fandral?"

As he caught his breath, his words became less choppy. "We were just at the Bifrost, asking Heimdall about Thor," he told her, collapsing down in the grass beside her. "He is well, if you were wondering."

"I know," she replied, thinking it imprudent to say that she hadn't really been wondering at all. Not about Thor, at least.

Fandral heaved a sigh, his breathing finally coming back to his control. "Well, I was instructed to tell you all the same," he said. "Thor is on Midgard with his mortal friends. According to Heimdall, they have recently been confronted with a bit of a problem."

Sif groaned. "What sort of a problem?"

After a hesitation, Fandral simply said, "Loki."

Sitting up a little straighter, she contemplated this. "Heimdall told me that Loki was shielded from his view," she said.

"He was," Fandral was quick to reply, "and he still doesn't show signs of magic. Heimdall just happened to glance down unto Midgard to see Loki's face. It surprised him, I suppose – as much as Heimdall is able to be surprised, that is."

"And it's a problem?" Sif asked, recounting his earlier word choice.

He made a half-hearted face, saying, "Well, I understand he is being rather difficult. Making threats he intends to keep and the like."

She just stared at him. "Fandral, do you realize what you're saying? He cannot exactly run free and do as he pleases at the moment. He's serving sentence."

"Could he not have escaped?"

"No." Of that, Sif was certain. "Even if he could, he did not will it."

Fandral clearly knew better than to question Sif's claims, his silence acknowledging that she knew Loki better than he. Instead, he only asked, "What did Heimdall see, then? For he said it appeared in every aspect to be Loki himself."

The thought occurred to her the instant the question had left his lips. "How much credence do you give the rumors that Loki associated himself with the Chitauri during his last attack on Midgard?"

A cloud of confusion crossed his face. "Not much, in all truth," he said. "Loki is too smart to make such a mistake."

"I know for a fact that the whispers are true," she returned, remembering a conversation held through prison bars – a story told in confidence to one who knew more than any ever should. "Except they demanded Loki's help, not the other way round."

Fandral lowered his voice, eyes darting around them to ensure their solitude. "You surely don't think it to be a Scrimorus, do you?"

Sif's mouth suddenly felt far too dry. "I hope not," she responded quietly, "otherwise the mortals stand no chance at all."

"And Thor will be of no help," Fandral added. "He never could place a Scrimorus – not even when his very life depended upon it."

"The only one who ever could was Loki," Sif allowed, eyes catching Fandral's. "Even if it was only because he was so adept at conjuring replicas of himself. Still, his record was far from perfect."

He hissed out a slow breath. "We've no knowledge of his location regardless," he told her, bitterly resigned, but too oppressed by the heat to demonstrate it in any sort of animation.

She shook her head, feeling tired and weighted down by this unwarranted turn of events. "What, then, can we do?"

"Pray," came his reply. When she glanced up at him, he said, "Should these mortals indeed have a Chitauri Scrimorus in their midst, you know as well as I that they stand no chance at all."

*One more thing from me, Faye: I made up the name of the Chitauri mimics. Scrimorus is entirely my word, so I apologize if these things actually exist in comic canon and there's actually a name for them that I didn't know when I branded my own. I know the Skrulls, but because these are specifically Chitauri, I wanted them to have their own name. And I'm not good at making words up, so this one took some thought. It's sticking around for the rest of the fic, so have fun!