  In 1987 S Cappell and J Shaneson constructed an s-cobordism H from the
quaternionic 3-manifold Q to itself, and asked whether H or any of its covers
are trivial product cobordism? In this paper we study H, and in particular show
that its 8-fold cover is the product cobordism from S^3 to itself. We reduce
the triviality of H to a question about the 3-twist spun trefoil knot in S^4,
and also relate this to a question about a Fintushel-Stern knot surgery.
