The etymology for the name "Orpheus" is really hard to pin down. You can go to made-up reverse-engineered languages, the received wisdom of the anti-Esperanto: Proto-Indo-European (P.I.E.) gives us the passive verb orbhao-, "to be deprived," itself derived from the P.I.E. verb orbh-, "to put asunder, to separate." You can support it with the Greek orphe, "darkness," and the Greek orphanos (self-explanatory). Where it gets interesting is that you can jump thence to goao, "to lament, sing wildly, cast a spell." Which is to say, in a half-imaginary semantic web: once there was a boy named Orpheus who was defined by what he gave up. No, scratch that. Orpheus was a man defined by what was taken from him, but also the fact that he created magic everywhere he went. Without the sacrifice, there's no story, and without the story, you don't exist: his failure of faith is what gives him existence, at least for us today. You look back -- at the end of life -- and if you're not willing to give it up at that moment, you never deserved it in the first place. His sin wasn't in doubting or disobeying -- it was in being unwilling to touch magic and move on, to let beauty rest and end and die like everything else. He couldn't cut the cord, couldn't let it lie, couldn't be strong unto himself and say goodbye with his back straight. Couldn't handle the marks and cuts of change, or deal the cards again. The other side of grace is also grace, but it feels like dying most of the time, and this is for the following reason: it is.
Previously: the Doctor, his Companions Rose and Mickey, her fake dad Peter, and the Preachers Jake and Rickey were surrounded by Cybermen on the lawn of the Tyler mansion, about to be deleted. Steel Jackie was stuck inside the house, Cybermen everywhere. Now there are credits, episode by Tom MacRae, and the Doctor pointing the TARDIS battery at the Cybermen and shooting out a golden bolt that lights them up in a net -- everyone's connected, so everyone's alone -- light bouncing from one to another, finally disintegrating them all. He shrugs at Rickey and tells everybody to run. Mrs. Moore pulls up in the Preacher van, honking, and they all pile in. The Doctor has to keep Pete from trying to run back in the house and save Jackie. That is to say, the Doctor steps in and stops Pete from turning around and trying to get his dead lover back: "Anyone inside that house is dead. If you wanna help, then don't let her die for nothing. You've gotta come with us right now." Pete nods and, face-forward, heads with him to the van. Rose is another story -- that's her sin, always; watch -- and the Doctor snags her, quiet but urgent: "Rose, she's not your mother." As Mrs. Moore yells at them that it's the slowest getaway she's ever seen, and drives away, Rose says she knows it's not the "real" Jackie, but it's interesting, because it's a different thing than with Pete. Her complex attractions to these two strangers are very different things: one has to do with memory (Jackie's twin) and the other with fantasy (the twin of a person who never really existed for her). And memory and fantasy are two very different things, if you're doing it right.