When my college students wrote about Hemingway’s story “Soldier’s Home,” many of them failed to show the possessive case of Krebs. It is tricky to show the possessive case of words that end in “s.”
You can choose either of the following forms to show possession of the name Krebs:
When you talk about Krebs’s mother, you could either write Krebs’ mother or Krebs’s mother.
The same would be true about punctuating Krebs’s nightmare.
Krebs’s worst nightmare had not yet begun.
Krebs’ worst nightmare had not yet begun.
Of course, use an apostrophe and “s” with Soldier in “Soldier’s Home” and Hemingway in Hemingway’s story.