Panel 1: It's nightime at the Pattermanse so naturally we have Elly shouting at her kids. To be specific, she's telling Mike to put his toys away because she says so. She's holding Lizzie as as does so which will do wonders for her hearing.
Panel 2: She then shouts that he has to get into his PJs RIGHT NOW IF YOU KNOW WHAT'S GOOD FOR YOU!! while plopping Baby Nizzie into her crib.
Panel 3: Lizzie, of course, wants to be reassured that she isn't the cause of this screaming match and plainitively asks "Mama." Elly's response? She shouts go to sleep. NOW!!
Panel 4: She then angrily slams the door behind her. Nice. That'll make everything better. No wonder Liz grew up messed up.
Panel 5: She then tells Mike he'd beter not make any noise tonight OR ELSE. I wonder what touched her off this time. Did he chew too loudly? Did he rhyme the letter "Z" with "tea" instead of "head"? Pull Liz's hair? Who knows what he did because anything he does gets her into a rage. That explains why he's screwed up.
Panel 6: We mext see her at the kitchen table bent down from the day's (self-induced) frustrations, sighing audibly.
Panel 7: She then goes back into Lizzie's room to check up on her.
Panel 8: Now that she's had time to calm down, she admits that she's got children most people would envy.
Panel 9: Too bad, she tearfully says, they wound up stuck with a crappy mother like her. It's also too bad that her remorse does no good; if it were to have served a purpose, she'd have changed her ways and been less fractious in the future.
Hypothesis: dantheman is right when he says that this was originally harmless-enough fluff. Back when Lynn first wrote it, it was clearly supposed to be an unusually bad day in Elly's otherwise orderly, happy life. Viewed through the prism of years of flapping, honking and telephone book eating, however, it's far less benign.