The investigation has been going on for months, and we're still 'none the wiser' about the true cause of the accident. [=we still don't know anything more about the true cause]
I'm 'wise to' you. = I'm 'wise to' what you're doing. [=I know what you're doing; I know that you are trying to do something dishonest]
I borrowed his car and returned it, and he was 'none the wiser'. [=he did not know that I had borrowed his car]
(..) COWARD!!! Potter? I know that many of you will want to fight. Some of you may even think that to fight is wise. Give me Harry Potter, and I shall leave Hogwarts untouched. Give me Harry Potter, and you will be rewarded. What're you waiting for? (..)2011 Harry Potter and the Deathly Hallows: Part 2