Panel 1: We find ourselves watching Liz and Mike return home from school. Mike notes that Mom is at work and asks Liz if she's got her house key. Liz says "Uh-huh."
Panel 2: When Mike calls Liz's attention to how great Farley looks, Liz points out the note on the end table. You will notice that Liz thoughtlessly left the door wide the Hell open because her brain can only handle one task at a time and has also been accidentally taught to let the dog go out whenever he gets to the door.
Panel 3: The note says "Dear kids, I've just had the dog groomed. Please don't let him get dirty! I'll be home soon. Love, Mom."
Panel 4: When Mike asks where Farley is, a panicked Liz stands next to the door she didn't think to close and tells him that he's out getting dirty.
Summary: This strip makes a nonsense of John's idiotic comment about how they can't prevent Farley from roaming around in the muck because, boy, howdy, was it ever preventable. All it would have taken is for Elly to put the note telling the kids she was taking the dog to the pet salon and didn't want him roaming around outside on the door so that they'd know to keep it closed. Since that would require her to understand that people can't read her damned mind, the inevitable result is Liz not knowing to close the door and her getting yelled at.
Come to think of it, it also makes a nonsense of any sort of claim that this is happening in the present day because most kids have cell phones and Elly could have simply texted them....unless, of course, she's one of those people who don't hold with giving kids cell phones. Maybe that's what this one's notes will be about.