It's a line we don't cross Jonty!

Walking Jonty in the park is a leisurely business, no dashing about chasing balls like he used to, or like the old Jack Russel that he had been watching today. He totally lost interest in retrieving things a few years ago.
I might not have thought of the title that I used but I'm nearly finished watching 'The Fall' on Netflix. It's a police murder series set in Belfast, quite riveting, and the lady D.S. said to one of the senior officers that he'd 'crossed a line'. I won't tell you why in case you watch it.