"You caused an incursion and we're going to fix it... unless you're afraid". The Aftermath S4 Ep 8

Walnut Grove is about to collide with the real world....when real life historical figures Jesse and Frank James show up in town after a botched bank robbery.  Using the excuse of having Swamp Fever, the two men manage to remain hidden in a rental property while hiring Mary as their personal assistant to run errands in town.  Meanwhile, Mary is having a challenging time in school when she tries to understand the point of view of the Civil war from the South's Perspective.  Which gets a young fellow classmate, Bobby Ford, upset and his father isn't too far behind.  In the midst of it all, a group of Bounty Hunters have also arrived in town, with a witness, clamining to know that the James brothers are in town.  Not only that, they take over the town to try and flush out the criminals.  However, the law abiding men of Walnut Grove are remaining tight lipped about things and refuse to help.  And if that wasn't enough, Mary decides to thank Frank James (aka Andy Dobbs) for his input about the Civil War and ends up being taken hostage. Leave it to Charles and Jonathan Garvey to save Mary, free the town, humiliate the bounty hunters and let the bad guys get away.  It was 1876 at the end of Season 2 so why is it only September 1876 at the beginning of this episode in Season 4? Why is Laura barely even a supporting cast member in this episode?  Which is worse Mountain Fever or Swamp fever?