This paper argues for a novel explanation of the A/Ā distinction. Ā-movement involves a layering derivation (Thoms 2019), in which QTF elements (Question/Topic/Focus heads, Cable 2007) are added countercyclically to their DP complements. This is motivated by the need to prevent QTF elements, which are argued to be phase heads, from acting as intervenors for selection, case and agreement. This theory improves the empirical coverage of Cable's (2007) theory of pied-piping, allowing its distribution to follow from independent constraints on movement. It derives the Ban on Improper Movement, including its extension to surfing and diving paths, and explains why Ā-movement cannot feed case or agreement. Finally, the theory is used to explain why Ā-movement, but not A-movement, must reconstruct for Principle C.