“Mush!” Victoria cried from her new position atop the wheelbarrow. Coco pushed back up to her feet and braced to bear her new load.

The first official obstacle on the Oregon Trail was disease. They arrived at a sign shaped like a gravestone that read DISEASE. A ghost popped up from behind the sign.

“I am the Spirit of Multiple Diseases,” said the ghost.

Some of the families screamed. But it was obvious from the Long Island accent and red plastic glasses worn over the eyeholes in the sheet that the Spirit of Multiple Diseases was Ms. Goldberg. She pointed a long finger at random family members.

“Dysentery,” she said. “Yellow fever. Dysentery. Scarlet fever. Yellow fever. Scarlet fever. Dysentery.”

The chosen family members grabbed their hearts. Both Bell children were picked for yellow fever. Coco was given scarlet fever. Victoria, in the wheelbarrow, was selected for dysentery.

“Now,” Ms. Goldberg said. “If your name starts with a letter between A and E, your disease is mild. You survive to live another day. Congratulations.”

Shrieks of laughter and manic clapping rose among the mild sufferers. Coco’s heart lifted, though she didn’t join the cheers.

“If your first name begins with F to O, your disease is moderate. You live.”

The group of moderates included Coco’s ex-child Marley. She and the other moderate sufferers celebrated.

“Ah,” said Ms. Goldberg. “But wait. You live, but unlike the mild sufferers, you do not escape unscathed. For the remainder of the journey, you must march with one leg dragging. The choice of leg is up to you, but it must always be behind you.”

Marley said, “That’s bull!”

“And now for P to Z,” said Ms. Goldberg. “Are you children prepared for your fate?”

“Oh God,” moaned Victoria from the wheelbarrow. “I don’t want to limp all day in the sun.”

Victoria wouldn’t be doing much limping, perched as she was on the rations. Even if both her feet were struck down, Coco would keep yanking her along.

“Severe sufferers,” Ms. Goldberg said. “You are dead. Please step forward.”

Victoria deserted the wheelbarrow, lightening the load so fast that Coco’s back snapped straight. Coco’s ex-child Peter also marched forward, along with several other sufferers. They stood before Ms. Goldberg.

“Join your mass grave.”

The severe sufferers lay down in front of the gravestone sign, the bottoms of their feet wagging at the survivors. Coco tried not to rejoice at their fate. Smiling with her headgear hurt, anyway.

“March on, brave pioneers,” Ms. Goldberg said to the remaining party. “But march with heavy hearts.”

The Oregon Trail wound down to the rim of the woodlands. There the party turned and marched along the tree line. Past the monkey bars and swing set, a creek cut through the playground. The creek was three inches deep, and children were forever damming it up, opposed, for some reason, to its free flow. Full of rocks and pine needles, the creek was rendered even shallower than its already pathetic potential. But still, parents rallied against it, claiming children could drown in an inch of water. Coco had squatted at the creek before, placing her face as close as possible to the surface. Thin water slid over mud, blurring her vision. All she’d have to do was push her nose in.