Harry turned his mind away from that chain of thought before it completely broke his resistance to the fear, because he couldn't think of feeding Professor Quirrell to Dementors while staying resolved against Death, it was a cognitive impossibility.
And Harry went on cutting the hole in the wall. He was using partial Transfiguration on a thin cylindrical shell of metal, two meters in diameter and half a millimeter thick, running all the way through the wall. He was Transfiguring that half-millimeter thickness of metal into motor oil. Motor oil was a liquid and you weren't to Transfigure liquids because they might evaporate, but he and Bellatrix and the snake all had Bubble-Head Charms. And Harry would cast Finite on the oil immediately after, dispelling his own Transfiguration...
...as soon as the separated and lubricated hunk of metal slid out of the wall and onto the floor of their cell, he'd slanted it so gravity would pull it in, once the Transfiguration was done.
If Harry and Bellatrix
Harry's brain suggested that he could try to Transfigure a surface cover over the hole in the wall, leaving a space for Bellatrix and Professor Quirrell to hide in, wearing the Cloak, while Harry turned himself in. And Professor Quirrell would eventually wake up, and he and Bellatrix could try to figure out how to exit Azkaban on their own.
It was, first of all, a dumb idea, and second, there would still be a huge hunk of metal on the floor of the cell, which would give it away.
And then Harry's brain saw the obvious.
Bellatrix and Professor Quirrell were the ones whose lives were at stake.
They were gaining, not losing, from taking the risk.
And there was no reason, no sane reason at all, for Harry to go with them.
A calm came over Harry as he thought it, the cold and darkness that had been wavering around the fringes of his mind retreated. Yes, that was it, that was the creative outside-the-box route, that was the hidden third alternative. The falseness of the dilemma was obvious in retrospect. If Harry turned himself in, he
Harry didn't even need to face the embarrassment of admitting he'd been tricked, if he ordered Bellatrix to remove the memory. Everyone would just assume he'd been kidnapped, including Harry himself. Admittedly, there was no plausible reason why the Dark Lord would ever ask Bellatrix to do that; but Harry could simply smile and tell Bellatrix she wasn't allowed to know, and that would be that...
Her Auror team had gotten around three-quarters of the way down Azkaban, as had the other two teams on the other two spirals. Amelia was feeling tenser already, though she was betting on the criminals hiding on the second-to-lowest floor, part of her wished Dumbledore had thought to check that specific floor more carefully and part of her was glad he hadn't.
And then there was a distant sound, like a tiny 'tink' noise coming from far away. Like a very loud sound coming from the second-to-lowest floor, say.
Amelia looked at Dumbledore before she realized, before she managed to stop herself.
The old wizard shrugged, gave her a small smile, said, 'Since you asked it, Amelia,' and went off yet again.
'
It seemed very...
The light from outside coming in... wasn't exactly the Sun shining on his face, but it was brighter than anything of Azkaban's interior.
Harry
If Harry stayed behind and turned himself in... then even if everyone assumed Harry had been a hostage, assumed Harry had lied to Professor McGonagall's Patronus at wandpoint... even if Harry himself got off lightly, well...
It wasn't likely that the Defense Professor would go on teaching at Hogwarts.
Professor Quirrell would have reached the predestined end of his career, in February of the school year.
And yes, Professor McGonagall would kill Harry, and yes, it would be slow and painful.
But staying behind was the sensible, safe,
Harry turned to Bellatrix; he opened his mouth to instruct her a final time -