After seven whole episodes, Hipster Spock - played by Gregory Peck's grandson, Ethan Peck - finally arrives into the series, but there isn't much for him to do.
In fact, what 'Light and Shadows' really does is pad out the season's fourteen-episode commitment in a way we haven't seen so far. Let's be clear - there can be self-contained episodes where, sgenerure, everything's wrapped up at the end of the episode. You journey through an entire arc, and the characters come out the other end of it and it shapes both your perception of them and develops them further.
That's why when you look at classic episodes from 'The Next Generation', like, say, 'The Inner Light' or even 'Far Beyond The Stars' in 'Deep Space Nine', they're self-contained but they shape how we perceive the characters. A "filler" episode is exactly the opposite. Whether the story is self-contained is irrelevant, because nothing really moves forward. It's just standing in the same spot, waiting for the season to move ahead so it can catch up behind it.
To be clear, 'Light and Shadows' plays itself out like a soap opera episode. Michael Burnham (Sonnequa Martin-Green) arrives on Vulcan to help with the search for Hipster Spock, believing that her foster parents are hiding information about his whereabouts. Sure enough, she convinces Amanda (Mia Kirshner) to bring him to the temple where Spock is hiding as his mental state further deteriorates. Believing him to be innocent, it's only when Sarek (James Frain) rocks up and discovers that Amanda's been hiding him that anything happens.
From there, Hipster Spock and Michael bring him to Section 31, believing that they have the best technology available that unscramble his mind and give him some form of clarity. Right here is where, to be honest, the episode just goes off the rails.
As the past few episodes we've seen on 'Discovery' have shown, Section 31 is being revised from what we understood it to be in other 'Trek' series to what it is in this one. It's gone from a dangerous, unaccountable paramilitary organisation that frequently flouts the law in order to do whatever it deems necessary to preserve the Federation - to, basically, a bunch of space goths who are little bit devious, and seem to hoover up misfits to help them in their cause.
Yet, this episode finally seems to be shifting back to what we already knew - that Section 31 are not only devious, but that they're almost always the bad guys in any situation. With the help of Emperor / Captain Georgiou, they affect an escape from Section 31's ship and wait for the search parties to disappear - all before Michael finally figures out what's happened to Spock, and why he keeps repeating a series of numbers. The numbers are coordinates, and point to a planet called Talos IV - a major plot-point in classic 'Trek' episodes, 'The Cage', and 'The Menagerie, Part I & II'.
The B-plot, meanwhile, saw Captain Pike and Ash Tyler get caught up in a time-loop that had all the bearing of a hastily spliced together idea that was really just there to keep the action up whilst the soap opera shenanigans played out Hipster Spock and Michael.
Now seven episodes in, you can't expect every episode of 'Discovery' to be a winner. After all, 'The Next Generation' had at least two full seasons that were total write-offs and are largely ignored when discussing the series. By referencing major episodes from the original series, the story is clearly building towards something and if an episode is needed to set the table for it, so be it.
The pay-off, however, has got to be worth it as on its own, 'Light and Shadows' is the poorest episode of the series so far.