You Tripped at Every Step Lyrics

Lyric discussion by CoffeeStains 

Cover art for You Tripped at Every Step lyrics by Elvis Costello

OK, this has to be about incest, doesn't it. I don't understand all the references, but I am assuming that Elvis is talking about the torment that both the father and the daughter are going through--they are walking this knife's edge knowing that sooner or later everything will become known to mom and then their life, as disturbing as it is, will change forever. What's the "cartoon mouse" line about?