Honestly, I wouldnt be surprised if Idris is just as fond of Bill as we are.
Its chained and in pain, presumably having been kept this way for years.
The sight is haunting both to Bill and the viewer.

Credit: Simon Ridgway/BBC America
After all, how else would someone display this much lack of compassion?
Like I said,scumbag.
Thankfully, the Time Lord and his companion quickly manage to fish out the sonic screwdriver.

Simon Ridgeway/BBC America
But before he can really free them, the Man With the Ship Tattoo arrives and confiscates it.
Just before he falls through the ice, Tattoo Man tosses the Doctor the sonic screwdriver.
Now free, Bill recruits the street kids to help reset the ice.
Only when he does set it off, it doesnt work like he planned.
and place all the explosives by the chains trapping the fish.
With that, Tiny swims off to freedom, with Bill grinning at how happy she sounds.
As for the kids?
(Because apparently, girls arent eligible.
But I suppose, one social issue at a time.)
The Doctor credits this to Bill, whose order it was to do so.
And seeing acertainsomeoneis returning this season, this might not be too wild a theory at the moment.
(See Exhibit A, below.)
But as the Doctor explains, hes 2000 years old, heneedsto move on so more people wont die.
(To be fair, she did witness achilddie.)
Its measured by the value you place on a life, an unimportant life.
A life without privilege.
Thats what defines an age.
Thats what defines a species.
Thats something for us to do on our own.
Or in this case, Bill.
And to the shows credit, it does not shy away from that issue at all.
Bit more black than they show in the movies.The Doctor:So was Jesus.
(EvenDoctor Whohas had some trouble with it in the past.)
Heres hoping he tags along and we get more answers about that door next week!