what the devil does a mentor do 又是does,又是do呢？怎么理解这句意思？

I glanced at him with surprise. His cordial agreement with all I said cut the ground from under my feet. It made my position complicated, not to say ludicrous. I was prepared to be persuasive, touching, and hortatory, admonitory and expostulating, if need be vituperative even, indignant and sarcastic; but what the devil does a mentor do when the sinner makes no bones about confessing his sin? I had no experience, since my own practice has always been to deny everything.

老师： but what the devil does a mentor do 这里没看懂，怎么又是does,又是do呢？怎么理解这句意思？