The Express Bus to Crazy Town

Let me tell you something about my dad.  He was in the Navy during WWII and he is a retired firefighter. Those two facts should tell you a great deal of the kind of man he is.....proud, independent, tough.  So trying to help him is a delicate dance; the old two steps forward, one step back.
When my dad first began to fail, my sister and I swooped in determined to help set him right as only two people who have spent their lives in the helping professions can do.  We made appointments for hearing aids, the doctor, OT and PT.  Because we felt he could no longer be by himself, one of us began to stay with him all the time.  He had basically stopped eating and was pretty much living on a cup of milk a day, so we started to cook him dinner every night.
In the space of a few weeks my dad rejected his hearing aids saying that he can now hear just fine.  He told the PT and OT not to come back anymore.
Last weekend, my sister and I planned a couple of days away.  A little vacation with a girlfriend.  A time to shop and walk on the beach and relax. 
 As my dad had fallen four times in the past two weeks, we discussed with him that we really didn't feel he could be alone anymore.  He agreed. And then would disagree a few hours later.
My sister had a friend of her daughter come to spend the weekend with him.  Hours before we left, my dad and my sister had a huge fight over this.  My sister told me that she thought she had won.
We left and spent most of the weekend talking about my dad.
On Sunday I began getting phone calls.  My sister's friend was, in his words, about to worry him to death.  He wanted her out.  If she wouldn't leave, he was leaving.
"Do you really think he will leave?" I asked my sister.
"No, he can't get out of the house by himself anymore.  He can barely make it to the bathroom using his walker." said my sister.
A little later, my sister got a phone call.  Dad had left. Using his cane. He drove away in his car.
We called his lady friend and she found him and got to go home.  Thank God, he didn't kill anyone while driving.
How do you help someone who refuses to admit that he needs help?  How do you help someone who tells you over and over how depressed he is, but then won't make any changes to make his situation better?
Oh, we did get him to the podiatrist and had his nail cut.  I guess that's something.