After half a bottle of firewhiskey, Remus starts to beg her.
After three quarters of a bottle, Tonks agrees.
Remus closes his eyes to her transformation, and then Sirius is there, slouched and heartbreaking.
He looks different, and for a second Remus thinks Tonks got it wrong. But it's just the expression, that deep sadness in his eyes replacing edgy frustation.
He looks even sadder when Remus starts to cry. He holds Remus, whispers love-words that Sirius could never say, and Remus sleeps in his arms.
Remus wakes hungover, alone, and he doesn't know which of them he hates more.