The fragile truce between the Winchester brothers is tested again when Sam unearths a possible case for them to investigate, but Dean has become increasingly obsessed with tracking down Abaddon after killing Magnus with the First Blade in Blade Runners.
While Sam heads off, Dean is struggling to cope with the side effects of using the Mark of Cain, and when he can't find answers at the bottom of a bottle, he begrudgingly turns to Crowley - who is more than willing to offer support!
The violent murders that Sam is looking into are proving difficult to crack until he meets Julia Wilkinson (Jenny O'Hara), an ex-nun, who tells him about an undercover visit to the town decades ago by the Men of Letters - in the form of Sam's grandfather Henry (Gil McKinney) and Josie Sands (Alaina Huffman) - the future host of Abaddon.
As Julia's tale progresses, it becomes clear that we are hearing the origin story of the Josie-era Abaddon, and the fact that Abaddon let a witness to her transition survive is the the one slight weakness in this story.
Of course, if she hadn't, then we wouldn't have had a story and Sam wouldn't have unearthed the latest element in the Knight of Hell's masterplan for domination of the infernal realm.
Minor flaw aside, Mother's Little Helper is yet another powerful episode, really driving the the main season arc forward, giving us insight into Abaddon's schemes while simultaneously revealing - without going into the details - that Crowley is, unsurprisingly, playing Dean.
To what end? Who knows? But it's sure to be an interesting ride with an unhappy ending for someone.