Panel 2: Another dramatic pose. They could very well be looking up at a hostile spaceship, with Liz telling Ellen not to panic. Even the background looks like they're on a hillside, with the sky turning an unnatural color.
Panel 3: Calm down, Liz; Morsel's not here yet. One exclamation point will do.
Panels 4-5: Okay, another Miss Edwards flashback. Once, the class was doing a lab that involved solutions of salt water and sugar water. The students bombarded her with questions and complaints -- "I spilled mine; can I start over?" "Yuck! Tastes terrible!" "What's an ion?" and finally she responded to "What's 'saturation point'?" with "Saturation point is when you absolutely can't take any more!"
"Cool." "Right." "I knew that."
I've long since accepted Lynn working backwards from the punch line, but it could have been one of the students being "lost", not Liz. This should not. be. so. difficult for her.