Malcolm lets King Duncan know that Cawdor did confess his treason before he died, so th. This is good for Cawdor because they believed back then that if a person didn't confess before they died then they wouldn't be admitted to heaven. Duncan loved the Thane of Cawdor but had to have him killed for betraying him. Duncan is sad at the news, but contemplates how he did trust the man; sadly, he says, "There's no art/ To find the mind's construction in the face" (I.iv.12-13). This means that even though a person can be trusted by the smiles they give or the faithful words that they promise, but no one can determine what is going on in the mind. Friendships and relationships are tricky things, especially when one friend is tempted by power, greed and glory. Also, it is tough to catch a liar.