Check the penultimate panel for an extra pair of feet in the foreground. The ultimate panel has a wisp of unearthly smoke in the doorway as well, likely Danny fleeing. Maddie might not know that he's alive, but it's also possible that he's gone off to die, or mend himself in privacy and safety. Or it's possible that the remaining human portion of himself died in that room and all that's left is the fractured half of his ghost form.
But Danny's secret is out at any rate - and then Maddie will have to come to terms with what her hobby (job?) has done to her children, and how cruel she has been to real, sentient beings whom she has hunted for years. Beings that include her child.
Considering the wisp of green smoke in the ultimate panel, I assume that was Danny standing behind her and fleeing, but now that I think about it, it very well may have been Vlad or any other ghost, friend or foe.
I don't think Danny is invisible in the puddle of blood and ecto-blood; Maddie was wearing her Fenton-goggles when she first looked in the room. She would have seen Danny were he invisible, which leads me back to thinking it was Danny fleeing the scene.
Sorry for not getting back to you earlier. The wisp of green smoke was likely Danny. Judging by that pool of blood, and the general atmosphere of the comic, Danny was probably killed. But that leaves me to wonder where his human body went??
Her goggles allow her to see ghosts that are invisible? Why did I not know that? Lol
Merry Christmas? well this is interesting as a possible plot twist in the realization that her son is the ghost she has been trying to hunt all this time. I wonder who it was standing in the doorway.....awesome none the less.