Bellatrix might have told him that she didn't want him inside due to wanting to have warning should someone interrupt them, but Crouch knew better. In reality, Bellatrix knew that he was, besides his smarts, also incredibly sadistic. She clearly did want to have the lion's share of the fun and thus gave him guard duty to make sure. Oh, he didn't mind, as he was patient and could wait.
Truth to be told, he was disturbed that the Dark Lord had vanished, due to Lord Voldemort giving him the appreciation his father had denied him. He had only been in his employ for a short time, but already proven his worth. The Dark Lord had forbidden him to do anything high-profile, stating that he needed him to be able to keep up the pretense, so that the strike against Crouch Senior would be all the more satisfying once the time came. Thus why his vest, for a Death Eater, was still quite clean.
He thought in disgust at these pathetic, opportunistic worms like Lucius Malfoy, who clearly couldn't be fast enough to forsake their Master and come up the the cheap excuse they had been under the Imperius Curse and thus weren't responsible for any of it. However, their cowardly ways also gave him ideas. Should things go wrong, he could t least make sure his cold father would suffer as well.
"Ouuuuaaah!" "Yaaaargh!"
Hearing screaming from the inside, he knew that Bellatrix lost her slim patience with the Longbottoms and the fun part had started.
Really too bad I couldn't be part of it. However, perhaps this is for the better. Already planning ahead, he moved further away, so he wouldn't hear the screams anymore. Plausible deniability after all.
Several minutes later, Bellatrix paused a moment to catch her breath. Casting Crucio at two people at the same time, thus needing to split her attention and hatred, was a bit tiring.
The Longbottoms had felt pain like never before - a pain so intense that they had honestly wished to die. However, they had managed to stay firm and not reveal any of the little they did know. The magical bindings had been removed, clearly the Death Eaters no longer felt their victims were in any condition to try and escape. They paid no attention to Frank Logbottom's shaking hand trying to reach for something in his other sleeve.
"Hey, Bellatrix," Rabastan called to his sister-in-law.
"Yes?!" Bellatrix barked, starting to get frustrated that she was getting nowhere. If that continued, she would Crucio them until they were drooling idiots.
Rabastan would never openly admit it, but Bellatrix intimidated him. "Making them just feel pain doesn't seem to work. Maybe all of us together should put more variation into it? You know, use our imagination?"
"Yes, we are not exactly one-trick ponies, are we?" Rodolphus added, knowing what his brother was playing at.
"Hmmm... yes." After a few moments, Bellatrix understood the appeal. "Well, then, wands out, men!"
She then turned back to the Longbottoms, giving them a mockingly disappointed look. "Oh, both of you did not play along and told us what we wanted to hear. You have no one to blame but yourselves for what is coming next. Of course, unless you finally want to spill it?"
Alice's mouth by now had become quite bloody from biting the insides of her mouth. "Go to hell, Lestrange," she spat.
"Now look what you have done..." All three Death Eaters raised their wands.
Frank barely managed to finally get the small glass sphere out of his sleeve and break it in his hand, before things became worse.
It was perhaps just a minute, but all three of the Lestranges now seemed to be in a competition who could be the most sadistic with dark and injuring spells. The Longbottoms in some moments even wished they 'only' would have been under the Cruciatus Curse. That wouldn't have been as bad as what they were suffering now. Death really would have been a mercy at this point.
Thankfully, the torment did end suddenly.
"Hands up!" "Wands away!" "Don't move!"
It came all of a sudden; Aurors stormed into the ruin, at least a dozen of them. And they took no chances, considering who it was they were encountering. The Lestanges had little time to react, before stunners rained onto them, overwhelming their defenses. Overkill was better than letting them escape, and they only had this one chance while the Death Eaters were distracted.
"Secure them, lads!" the leader commanded.
The leader, Alastor 'Mad-Eye' Moody truly was an intimidating sight. Having lost a leg and part of his face in battle against Death Eaters only served to make him look even more determined than he already was. The magical replacement eye in one of his eye sockets, which unnervingly could see through his own head, only added to his aura of sheer power. That new eye was a recent development after a nasty battle.
"Yes, Sir!" they told their commander. His sheer accomplishments - and the way he got disfigured in the line of duty - instilled great respect to the men in their ranks.
"Damn, this looks bad!" Moody cursed when seeing the state the Longbottoms were in. Without him insisting everyone should still carry their emergency signals, these two probably would have died. "What are you waiting for?! Get them to St. Mungo's right away!" he barked his orders.
The Longbottoms were taken away to the emergency room, while Moody approached the reawakened and properly restrained Lestranges. "Death Eater scum... Even without your Master, who has bitten the dust, the only thing you can cause is more suffering. Caught red-handed, no way to talk your way out of it."
For someone getting arrested, Bellatrix looked incredibly arrogant. "This is just a temporary setback. the Dark Lord will rise again, you better believe it!"
Moody's magical eye seemed to stare a hole into her. "If that's your illusion, who am I to take it from you?"