  This paper proves the local Langlands conjecture for the non quasi-split
inner form Sp(1,1) of Sp(4) over a p-adic field of characteristic 0, by
studying the restriction of representations from the non quasi-split inner form
GSp(1,1) of GSp(4) to Sp(1,1). The L-packets for Sp(1,1) are constructed based
on the earlier work on the local Langlands correspondence for GSp(1,1) by Gan
and Tantono. To parameterize them in terms of so-called S-groups, we establish
and utilize the local Langlands correspondence for reductive dual groups which
participate in the theta correspondence with Sp(1,1) and GSp(1,1). An
interesting phenomenon arises when two distinct members in an L-packet of
GSp(1,1) are restricted to Sp(1,1).
