For the most part, the third season of ABC's Marvel Studios drama "Agents of S.H.I.E.L.D." has been running like a well-oiled machine. But this week, that machine took a surprising left turn -swerving away from some of the stories the show has been promising to pay off while simultaneously changing others forever.

This week's "Devils You Know" episode opens up on the seeming main thread of the season: Inhumans. Hiding out from the growing hunt to bag and tag their kind by the A.T.C.U., a pair of young Inhumans settle into a quite life of cooking dinner while flying around their apartment when they get a pop in from Alisha - the duplicating dynamo who played a big part in the raid of S.H.I.E.L.D. during last season's finale. The replicant tells the pair of pre fish oil Inhumans to be on guard for those out to destroy their kind...but it's all for naught. Moments after they mention a bizarre e-mail about Inhuman survival, the big dark dreaded Lash arrives to swiftly murder all three.

Even as Alisha survives in S.H.I.E.L.D. custody (the way she experiences her dupe's demise make it tough to call this a benefit of her powers), the story pushes forward into a juggling act of the various plotlines that have been rolling through the season. Coulson begrudgingly works more closely with A.T.C.U. on the Inhuman hunt while Daisey and Mack voice their dissent. May's former husband Dr. Garner skulks around the headquarters fretting over the outcome of their missions as people like Alisha are increasingly psychologically damaged. May herself returns to base for a few awkward reunions as she delivers word that Hunter is going all in on finding new Hydra "Director" Grant Ward. And through the background, tensions mount between Bobbi (worrying about Hunter), Simmons (hiding her goals from Fitz) and Fitz (worrying about Simmons).

On their own, all of these stories play a little rote. Any serial drama is going to have moments where its long term planning slows down to put all the proper pieces on the board, but without a really compelling original development to hang its hat on, an episode will easily start to feel like too much is going on but not enough is happening. For most of this week's hour, "Agents of S.H.I.E.L.D." makes it seem as though our Inhuman hunt will continue to be the main event, and so the audience watches it closely for any sign of real story development in a conflict that's been status quo since the premier.

They don't get much chance of that. While little details work fine -Daisy's rebellion against Coulson's decision-making and Coulson's own flirtatious relationship with A.T.C.U. Director Rosalind -the main investigation that takes the team from the virus-sprouting e-mail sent to Inhumans to a programmer who's unfortunate "power" is to break out in hives and migraines whenever one of his brethren is around drags. Though our computer wiz's predicament offers insight into Lash's mindset (he's killing Inhumans less as a punishment and more for some kind of strange protection mandate), the character is unmemorable and the outcome never really carries any weight in the big scheme of things. When Daisy sees Lash's shadow seemingly transform to a normal human shape after he waylays their transport, the show is almost sending a signal to the reader saying, "Yes, you'll have to wait another week to get any payoff." Luckily, that isn't necessarily the case.

On the other side of our show, everything involving May, Hunter and Ward feels like B-Plot. Hunter's climb up the Hydra ladder is motivated by his desire to get one back for Bobbi's injury last year, making him rash but likely not totally out of control yet. Back in the Hydra ranks, Ward's insistence on building up his organization to look and feel more like S.H.I.E.L.D. is the latest and sharpest reminder that more than anything, he wants back into the heroic organization where he once felt at home. Meanwhile, May's own homecoming feels tertiary at best. Her avoidance of dealing with any real issues with either Coulson or Garner seems to be another piece of the puzzle waiting for payoff at a later date.

But when Hunter finally lands in Ward's lap (and is immediately identified as a S.H.I.E.L.D. double agent), even May's cavalry arrival can't stop the worst from happening. In one of the strongest twists the series has pulled off since the Hydra boss' own "Winter Soldier" defection, Ward turns over a card May didn't see coming: at any moment he can kill Garner thanks to a well placed young recruit from the Strucker family. If they let Ward go, he promises Garner lives. It's not enough for Hunter who both wants Ward's head and can't stomach Hydra getting away with a cache of guns he gave them while climbing the ranks, so the agent takes the risk that it's all a bluff and fails badly. Ward escapes with one bullet in the shoulder, and Dr. Garner is seemingly slashed then exploded by the young Strucker.

By inverting its two major plotlines at episode's end, the series producers earn a lot of good will in the face of a season that's had its moments but still dragged a bit. A spy series should first and foremost feel unpredictable, and the shell game that led to Garner's death delivers that far above anything dealing with the Inhumans or Simmons' interplanetary PTSD. As with the end of Season 1 and the start of Season 2, "Agents of S.H.I.E.L.D." is at its best when it leans into its "Mission: Impossible" roots rather than rely on Marvel Universe Easter Eggs to draw in diehard fans.

This isn't a feet that can be replicated that often or that easily...and considering that next week we're returning to Simmons' struggles as the A-plot, it's unlikely the show will try a fake out like this again very soon. But if "Agents" works to continue a balancing act that alternates between superhero world-building and espionage shockers, we'll be willing to sweat out a few clunky plotting moments here and there to see where the fuse goes boom.