I remember being excited when you said about the starting point for this fic, and it more than lived up to expectations. Making Tonks the innocent deliverer of such an appalling discovery to the man she loves, and is wanting to help, is such an agonizing twist. No wonder her colour literally drains away with horror and worry at what is to come. "Will he want to—to—finish what he started?” and “From what I’ve heard, I think he’ll be more likely to welcome me into the fold.” is positively chilling from both of them. (I like that you've got in straight away that it's His Life she is terrified for.)

Love, love, love all the interaction between the hand holding, the hand withdrawing, the hands being sat on, and then the hand desperately reaching out for comfort only to find, of course, that Tonks's is immediately there for him. Aagh.

And I like how skilfully you've given Tonks a couple of very good reasons to be furious at Dumbledore, and to characteristically show it. Remus has even more, and characteristically chooses to rationalize it all away. Or does he? It must all add to the slowly bubbling cauldron at this stage.

As everyone has said, the pacing is excellent; it builds quietly to such a heart-wrenching climax. Dark times ahead for them both but a wonderful read for me.

Re the title: Cat Steven's Moonshadow came to mind, or perhaps it was the lyrics that did. But that's not remotely subtle and I like the one you chose.