Anders in the Fade is an Act 2 companion quest for Anders in Dragon Age II.
Acquisition
Anders in the Fade is available after completing Night Terrors if Hawke took Anders to the Fade and accepted the sloth demon Torpor's deal.
Walkthrough
Talk to Anders in his clinic in Darktown.
If Hawke honored the deal and helped Torpor to possess Feynriel, all dialogue options result in 
Anders: rivalry (+15). If a romance exists, Anders will end it, saying that Hawke should turn to Merrill since both like demons so much.
Alternatively, if Hawke did not honor the deal and subsequently killed Torpor, a special choice is available: informing Anders that the demon is dead and that siding with him was just a ruse results in 
Anders: friendship (+20). Hawke can also proceed with the romance.