brokenpromise Unfulfilled vow Evidence of unreliability Disappointment, often ... and a hint to this puzzle's theme Certain moral lapse, and a hint to what's hidden in this puzzle's theme answers Bad thing to give to a child "I do," for the divorced Description of 25- and 26-Across ... in 12-/35-Down Moral lapse that is reflected literally by the answers at 17-, 24-, 46- and 54-Across Result of not following through (of which there are four examples in this puzzle's grid) Description of 25- and 26