Too bad. Sherlock could have had another protege.

Cassie Lenue returned on Elementary Season 7 Episode 8.

Why? That changed by the minute with this pathological liar.

It was well into the second half before Sherlock determined Cassie's motivation. 

Cassie, who Sherlock and Joan sent away on Elementary Season 4 Episode 7, was among the last people they expected to find on their doorstep.

I loved Cassie's new last name, short for "last name unknown." What an inspired choice for the former foster child who didn't know her history.

Joan and Sherlock rightfully couldn't trust a word coming from her lying mouth.

But she did serve them up a worthwhile case: a woman Cassie claims was her former foster mother who had been gunned down while buying clothes for her current foster children.

Related: Elementary Season 7 Episode 7 Review: From Russia With Drugs

But by the time Sherlock determined that Cassie had just located an unsolved case that would suck them in, they were already involved in an engrossing mystery.

It's been a while since I was involved with baby formula, so it was a surprise that it was a substance in which people traffic.

People can make billions selling formula on the black market? That was amazing.

It was such a thing that New Jersey had an interagency racketeering investigation going, although not too well. 

Heather had agreed to be an informant in said investigation, but her being killed had caused it to stall.

So the New Jersey team was more than happy to pass it off to their New York brothers.

Cassie turned out to be a real secret weapon in this investigation.

First off, such a skilled liar can read people and tell if they are telling the truth.

She eliminated one murder suspect and flushed out the man who actually ordered Heather's murder, just based on her observations.

Cassie also has a future in loss prevention as she was able to pick out potential thieves on surveillance just based on their behavior.

Plus she proved she knew how to do research to back up her lives with so much truth as possible.

Still, Sherlock actually broke the case open when he figured out they were looking at the case wrong.

Related: 21 Characters Who Work Way Too Hard

This wasn't about a criminal organization eliminating a snitch in their midst.

Instead, it was a businessman smelling profit who was behind the murder.

See if I got this right: the state legislature getting rid of a subsidy for formula would reduce the amount of formula sold.

Which in turn was going to hurt the bottom line of grocery-store companies.

So the foster mom was killed to slow the investigation and the resultant need for investigative action.

And it had nothing to do with the baby-formula mob, which is a funny concept about which to think.

No wonder Gregson and Marcus were smirking while listening to the explanation of the case.

In the end, Cassie went off the rails, confronting a grocery-store magnate after breaking into his home and blackmailing him for $2 million not to tell.

Her setting up a meet with the owner quickly exposed his fixer, who was the state policeman in the middle of the investigation.

The end of the case seemed a little abrupt.

But the episode was less about the case than about the evolving relationship between Sherlock and Cassie.

Cassie was likely lying when she offhandedly told Joan that she was the result of a one-night stand between Sherlock and her mother.

But you had to wonder because the two seemed so much alike.

After suspicious Sherlock determined what Cassie's end game was, he sat her down and gave her the benefit of his experiences.

The essence of his talk was that Cassie didn't need to be alone but that she needed to find a way to channel her gifts for good.

And frankly, that's what she did from then on for the rest of the episode.

Sherlock was right there beside her, showing her how it's done.

It's a shame this episode was so late in the series. Otherwise, Cassie could have become the new Kitty.

It was a sweet ending, with Sherlock offering Cassie's history to her, only to have her reject that.

Then he followed that up with an application for a name change, with her, in turn, asking for his help to come up with her new name.

The downside of this episode was that with Cassie getting so much screen time, we saw precious little of Gregson or Marcus.

This marks the second consecutive self-contained episode.

While it was definitely enjoyable to continue this season's trend of revisiting favorite characters, neither recurring storyline was visited.

So we've learned nothing about Odin and the vigilante group he's part of or leading and nothing about the assistant FBI director who is blackmailing Sherlock.

Also, I'd like to get back to England for an episode or two in the five that remain, so we could visit with Morland and maybe even resurrect Mycroft.

Time is dwindling and there's still a lot of ground to cover.

Related: Get CBS All Access via Amazon Channels for Hit Shows, Exclusive Originals & Live TV! 

So enough with these one-offs. Let's push the pedal to the metal and go out in style.

There's been a lot of casting about, looking for a direction, with the only sure thing visiting with quite a few old guests.

That's not a bad thing, but it can't be the only thing.

To follow the meandering season, watch Elementary online.

Did you enjoy seeing Cassie again?

Could she actually be Sherlock's daughter?

What character (other than Moriarty) do you most want to see before Elementary finishes?

Comment below.

Dale McGarrigle is a staff writer for TV Fanatic. Follow him on X.