  A 10-dimensional symplectic moduli space of torsion sheaves on the cubic
4-fold is constructed. It parametrizes the stable rank 2 vector bundles on the
hypeplane sections of the cubic 4-fold which are obtained by Serre's
construction from normal elliptic quintics. The natural projection to the dual
projective 5-space parametrizing the hyperplane sections is a Lagrangian
fibration. The symplectic structure is closely related (and conjecturally, is
equal) to the quasi-symplectic one, induced by the Yoneda pairing on the moduli
space.
