Then even that desire to merge in Shiva disappears and there remains only the Will of the Lord. In other words, the involution that the jIva made with deliberate effort merges in that first evolution of Shiva. At that point, as far as that jIva is concerned, Shiva Himself, without expanding in evolution, involutes within Himself and receives the jIva into Him.
Think of a flood of flowing water. Put some object into it. The waves will toss it back and forth and push it over to the bank. This is natural. But when there is a great vortex in the current, it takes the object into itself and consumes it. This is what happens here also.