Odin offered Loki a chance.
When Thor brought him home, Thor led him, manacled and muzzled, as Odin had ordered it done, to the throne room.
Odin did not know Loki's will in these happenings. And he would not have Loki honey-tongue his way from Thor's grasp. Or, worse, take the cube and vanish back to whatever master had claimed him.
Abandoning his burden and without a backward glance, his open face dark with pain, Thor left them.
Odin had not watched them from his throne. He was weary. And he could not see his child fall into darkness again. Should he be lost, Odin had no desire to see it done. He would wait and he would gather what strength he well knew he would need for their return home.
He was not so young, as he had been. And his sleep had not given him rest as it had, so long ago.
And there were many other weights beside. Unrest seethed on the edges of the realms. Dangers without did not keep their distance as they had. Word of BiFrost's fall had spread. And Odin was drained with sending Thor even just the short way to Midgard.
Weariness hung a heavy mantle on old shoulders as he watched his elder son on his errand with the Stone to the Vaults.
Loki's eyes did not follow Thor as he left. They were poison-green and they flashed with seething emotions. Among them frustration, pain, fear, weariness.
It was a deep weariness, Odin judged. Loki had endured great strain. Odin thought it probable, with his son's pride taken into account, that Loki was barely keeping his feet.
Such was the boy's choice.
Odin ordered the muzzle removed.
Then, at his next order, the guards cut their stiff salute, and they stepped away.
Odin sat back.
"My son returns to me," he said at length, gripping the shaft of his spear. "A criminal, defeated, and bound."
Loki made no move to respond, but looked steadily at a place just above his head.
"Have you nothing to say in defense of your actions on Midgard?"
Loki looked at him one moment. Then he gestured with one manacled hand to his chest, "Me?" He blinked as though startled and shifted on his feet, "I'm sorry," he said, "I thought surely you'd already decided. No," his chin jerked upwards. "I have nothing to say to you."
Then he smiled, wide and shameless and Odin felt his old temper flare to life in his chest.
He had reason to believe that Loki had quite a bit more to say.
Odin took a long breath. His hand drew tighter on Gungnir.
"Perhaps," he decided, "a stay in the dungeons might loosen your tongue." He raised his chin. "Guards."
Proudly, Loki closed his teeth, though he seethed in the depths of his eyes.