[This is a review of Elementary season 4, episode 1. There will be SPOILERS.]

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One of the strengths of Elementary is how it flows from season finale to season premiere in surprising ways. At the start of season 3, Sherlock and Joan were still working out the details of the dissolution of their partnership. The series utilized a short time jump to put some distance between the two and to give the story time to discover who Joan and Sherlock were apart from one another and what it would take to see them reconcile. The move afforded Joan some much-needed agency in the series, and it also presented Sherlock in a new light – that of someone desperately in need of Joan on both a personal and professional level.

Although the two eventually reunited, season 3 ended with an unambiguous moment that was certain to have enormous ramifications. Whereas separating Joan and Sherlock was a temporary situation that benefitted the series in terms of redefining its core relationship, there was never any real doubt that Holmes and Watson would eventually work together again. The depiction of Sherlock relapsing and using heroin again, however, is slightly more than your typical up-and-back – though it could still work out that way – as it could be the catalyst for some serious changes, should the series wish to make them a permanent part of the ongoing narrative.

From the get-go, the story of 'The Past is Parent' is interested in the fallout of Sherlock's decision to use drugs and to assault Oscar Rankin, exploring everything from Holmes potentially being put behind bars to his losing his and Joan's consultancy with the NYPD to the arrival of his father – resulting in the terrific John Noble as "The Mr. Holmes," or, simply, one of the best casting decisions of the 2015 TV season. There are so many avenues of interest stemming from what occurred during the season 3 finale, the fact that the main thrust of the season 4 premiere feels like any other random midseason episode is of little consequence. Rather than put the episode's focus entirely on a slightly Robert Durst-y cold case, the premiere utilizes Sherlock and Joan's investigation to highlight the finality of their situation with the NYPD and the uncertainty of what's to come once that case is inevitably solved.

Jonny Lee Miller and Lucy Liu in Elementary Season 4 Episode 1

For a series that deals mostly in absolutes – as is the procedural way – Elementary is surprisingly smart when it comes to uncertainty. And the question hanging over Holmes and Watson, regarding their future as investigators, manages to become an effective source of tension for the season's first outing. While there is little doubt that Capt. Gregson and Det. Bell will still play a part in the week-to-week cases, the episode makes a case for the show shaking things up by keeping Sherlock and Joan away from the precinct and out of the police's affairs – at least directly. There is still a good chance the ship will be righted and the NYPD will eventually welcome its two consultants back, but for right now, the idea of Holmes and Watson working for some other entity or going independent could work to the series' advantage. It's only season 4, but every now and again it's not a bad idea to change up the formula a little bit and see what develops.

Mostly, though, 'The Past is Parent' works as a place-setting episode, assuring the audience that although he relapsed, Sherlock is taking his recovery seriously, attending meetings and generally being open about things with Joan. Everything he keeps from her eventually comes out in a way that underlines the strength of their relationship, as does her response. Sherlock's apology for getting her sacked from the NYPD by association is followed up with Joan telling him her interest in being an investigator stems from a desire to work with Sherlock Holmes, not necessarily the NYPD. While that is a small indication the series may be able to position the two characters away from the police department, it also suggests there are larger ramifications stemming from Sherlock's relapse than who the two will be working for.

John Noble in Elementary Season 4 Episode 1

Elementary has hinted at the sort of man Sherlock's father is since the series premiere, and while there have been plenty of opportunities to introduce him, it feels worth it to wait this long, since the timing worked out in such a way Noble could be brought on to fill the role. This isn't the first time a member of Sherlock's family has been introduced, but the less said about Mycroft's role the better. Besides, the elder Holmes represents something far more interesting in terms of the show's dynamic. Like it or not he is a figure of authority for Sherlock, and a presence that looms large, even when he's not standing atop the brownstone's like he's watching smoke billow out from Mount Doom.

It is a surprisingly low-key premiere, but it is one that offers a lot of promise in terms of the season's overarching narrative. Things have been suitably shaken up and 'The Past is Parent' doesn't wait for them to settle before moving on to another plot point. Leaving its characters in an uncertain situation, and introducing a potentially malignant presence like Sherlock's father into the mix gives the series a welcome sense of unpredictability, even if its just for the next few episodes.

As it enters season 4, Elementary feels more like an old friend returning than ever before. Each premiere seems to get pushed back more and more, as CBS uses the timeslot for NFL games throughout the month of October. Nevertheless, for fans of the series, the return of Sherlock Holmes and Joan Watson is typically worth the wait.

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Elementary continues next Thursday with 'Evidence of Things Not Seen' @10pm on CBS.