There are so many great parts about this song, "Watching the Detectives." The totally contagious guitar beat (it's got elements of reggae, which I love), the almost 'crooner' qualities of Costello's voice, the conversational style of the verses, that one little piano bit on "running down my spine," the notion of a "face like a magnet"...it's just all great. But, for me, this lyric takes the cake.
"You think you're alone until you realize you're in it
Now fear is here to stay, love is here for a visit
They call it instant justice when it's past the legal limit"
Also, I can never get enough of that photo of Elvis Costello, the one that appears on the album cover of "My Aim is True". I strive every day to be one-third as cool as Elvis Costello.