When Alastair brings Castiel to hell, Lucifer is pleased. His pleasure wanes when he sees the broken form Alastair is dragging. Madness fills Lucifer's eyes. If Alastair was any less faithful he would have been killed, then and there. Instead he is sentenced to two weeks of being the other demon's plaything.

Alastair doesn't complain. He glares hatefully at Castiel, instead. That changes when he sees Lucifer kneel over the insensate angel and bestow a kiss on his slack lips. He knows he is lucky to be alive after almost killing someone his master cares for.

During the two weeks he is being tortured, by lesser and unworthy demons, his mind often turns to Castiel and what Lucifer's love of the angel will mean for the demon hoard. When he returns to his Master's side, he find's Castiel sitting on Lucifer's lap, dressed in black leather and wearing a think black collar. He is looking at Lucifer with adoring eyes.

If Alastair had less of a sense of self-preservation, he would snort. If Castiel is weak enough to be corrupted in less than two weeks, than he represents no threat to Lucifer's plans. Alastair feels stupid for worrying over the ramifications of his presence. He turns away in disgust and doesn't see the knife Castiel plunges into his back.

He also doesn't see Castiel return to Lucifer's side, soaked in blood and smiling a smile of pure madness.