It's hard to tell if that really is Mark revising his escape plan in the first panel. He's got the preference for khakis. He's got that familiar pubic hair dangling off the middle of his head. It's gotta be Mark. It's just a little harder to tell than usual.
"Harder to tell than usual" is a common theme in every panel of this installment. It's hard to tell why dog tracks would indicate that Mark couldn't be too far away. It's even harder to gauge Sue's location or size in the third panel as she massages Pop on his so-so-busted tractor. Above all, it's hardest to tell when Pop will realize that time has erased every spark of physical and mental acuity in his fragile denim body. If I had to take a guess, that moment of clarity will come after he sticks a few more inches of hand into that sputtering engine.