The Invisible Woman has disappeared! Sue Richards - founding member of the Fantastic Four, Marveldom's first family - has gone missing. Luckily for her, X-Factor Investigations - the world's first (and only) mutant detective agency - is on the case. Following a trail of clues that lead them from the famed Baxter Building to the darkest corners of Dr. Doom's kingdom of Latveria, Jamie Madrox and his crack team soon find themselves hip-deep in the greatest mystery their agency has ever tackled. But what they uncover casts a grim shadow over the Fantastic Four. Can everyone's favorite sleuthing mutants solve the mystery of the vanishing super heroine before the FF falls to pieces? They'll have to make it out of Doom's stronghold alive first! Collecting X-FACTOR #200-203.