You will need to file a Motion and provide the court as much proof as possible (have people write affidavits saying what has been going on) and ask for a modification of the current parenting plan.
Modifications of parenting plans are only done if there is a substantial change in circumstance. Depending on the circumstances, being absent and not excersizing visitation could be one.
Unless the parent is currently using drugs or alcohol, I would guess in the end (after spending several thousands of dollars in attorney fees, guardian ad litem fees and such) the court would leave the parenting plan as is and put supervised visits in place for as long as it takes to get the child comfortable with the parent again.
Why don't you want the parent to see the child? How old is the child now? Would the other parent agree (without going to court) to some limited visits at a public place to start with?