  We show that the irreducible holomorphic symplectic eightfold Z associated to
a cubic fourfold Y not containing a plane is deformation-equivalent to the
Hilbert scheme of four points on a K3 surface. We do this by constructing for a
generic Pfaffian cubic Y a birational map Z ---> Hilb^4(X), where X is the K3
surface associated to Y by Beauville and Donagi. We interpret Z as a moduli
space of complexes on X and observe that at some point of Z, hence on a Zariski
open subset, the complex is just the ideal sheaf of four points.

Algebraic Geometry