Just a great episode of Chuck right there, as "Chuck vs. the Aisle of Terror" had everything I could ask for:

The Morgan/Casey odd couple dynamic; Chuck and Sarah getting along on a mission; Jeff and Lester doing ridiculous things; and a long-running storyline coming to the forefront.  It was definitely one of my one or two favorites of this fourth season.

Let's get right to the meat and potatoes of this episode, Mary Bartowski.  We went into the ep under the impression that she was a bad guy with Volkoff, but had a feeling that she was deep undercover.  Mama B admitted to her undercover role early on, and I thought "of course."  What was so great was that the show switched back and forth on this angle multiple times over the hour.

When Mary ruins the deal with Dr. Wheelwright and shoots Chuck in the chest, I was swung back to thinking she was a bad guy.  But, no, she admitted to Chuck that she knew he was wearing a vest. We come to find out, thanks to the spy work of Mr. John Casey, that she is, in fact, a rogue double agent. I am skeptical of this information and still am on record for thinking she's a good guy.

Now we can take a look at how the Chuck triple threat played out this week:

Comedy
Jeff and Lester were back on their game.  Whether it was Jeff putting down a deposit for unclaimed merchandise at the morgue, or his admission that he'd do anything for 30 dollars and a sandwich, it was all gold. Also, "is it a baby or is it a snail? I don't know.

Again, there were plenty of yucks from the bearded wonder.  He compared himself and Casey to Ross and Rachel.  He was very concerned about Chuck not ruining his appetite at the weapon sale.  And he was sure Mrs. B wasn't a bad guy because she made delicious lemon bars.  Also, there was this: "Apparently I'm quite the hot commodity in the spy world. Morgan Grimes, not just for the ladies anymore."

Action
Not much in the fighting department, but the amount of tension that came with the anticipation and act of Mrs. Bartowski shooting Chuck in the chest was enough to make up for it.  I mean, come on!  She shoots my Chuck, her son, in the chest.  I don't care if you know he's wearing a vest or not, that is some crazy guts she's got.

Heart
Let's start with the uplifting moment.  Mary's plea to Chuck in the car that nothing means more to her than him and Ellie.  Of course, this was somewhat foolish if Casey's intel of her being evil is correct.

On the heart-wrenching side of things, there was the sadness that Chuck, and the rest of us, felt as Mary told him that she didn't want to know anything about him.  I don't care if you are an undercover spy or not, you don't say that to the child that you left out in the cold when he was nine years old.

And does it get worse than that final scene?  The anticipation of Ellie about to see her mom for the first time in forever, combined with the fantastic "Dead Hearts" by Stars for the musical background, was absolutely riveting.  For Mary to be taken away by Sarah and Casey before the meeting took place?  Crushing.

Moving Forward
This can't be it for Mary Bartowski, right?  The whole Volkoff thing is still out there, so this has to come back to the forefront.  Will they let it stay dormant for awhile like they did between episode one and this week?  I'd guess yes, and if so, I like the idea.  Letting the long-running plot stay in the background for a few episodes and then bringing it back strong is a nice way to play things this season.

Other thoughts:

• The whole Mama Bartowski undercover/double agent thing reminded me of a great moment in I Spy when Owen Wilson and Eddie Murphy are confused about whether the hot girl is a double agent, or a pseudo double agent, or a triple agent.  These things get confusing.
• Chuck: You just hate saying goodbye like a normal person, don't you?  This is true of most television characters.  Saying farewell is unnecessary on telephones, but have you ever tried to do that in real life?  It is very difficult.
• I love Big Mike calling Morgan "boss."

Dan Forcella is a TV Fanatic Staff Writer. Follow him on Twitter.