Shadowhunters has spent the last three weeks brewing up some brilliant tension, be it through relationship breakdowns, new threats looming ever larger or just some good, old-fashioned drama. ‘A Problem of Memory’ may have delivered a Simon-centric episode that focused on the fallout of Simon and Clary’s relationship following that Seelie Court-commanded kiss between Clary and Jace, but it ended on a much darker note with Sebastian being revealed as both a demon and Valentine’s son, Jonathan. Between ‘Day of Atonement’ and its subsequent background-filling and this week’s ‘A Dark Reflection’ showcasing Jonathan and Valentine as a force and a threat to be reckoned with, these three episodes quickly proved to be a binge-watcher’s dream, delivering all of the high-stakes action and emotional consequences with none of the waiting.

First up was ‘A Problem of Memory’, which distracted from the forthcoming bombshell revelation by focusing on a plot arc that was always unlikely to have any lasting consequences. The overriding arc of this episode saw Simon as the main suspect in a mundane murder case after getting a little too drunk on plasma, but conserving that particular story was wrapped up neatly with no lasting consequence, it’s more likely to be remembered for Clary and Simon’s break-up – and Alberto Rosende breaking hearts as he portrayed a more vulnerable side to Simon than we’ve seen yet.

With Simon and Clary’s break-up though comes the reality that Simon is going to be less of a main player going forward, purely because he claims he needs time away from Clary and that takes him away from most of this show’s action. And if we needed any more proof of this then it came in the fact that stronger supporting storylines of the episode are already managing to take the attention away from Simon’s own story. Between Magnus opening up about his past to Alec, and Sebastian being caught in his lie and revealed as the twisted, violent individual he is, ‘A Problem of Memory’ did a lot to establish the darker turn Shadowhunters was about to take – and put to rest the idea of Clary and Simon as a couple for good.And so onto ‘Day of Atonement’ which wasted no time in planting the seeds for Simon’s side-arc to move along as he attended his family’s Yom Kippur dinner with Maia by his side and did very little else. Clary, meanwhile, was avoiding the discussion of her feelings for Jace by focusing on the mission at hand, which saw her angel powers kick in once again to portal the pair of them to Idris in search of the escaped Valentine. But despite a few brief Clary and Jace moments – and an actually-quite-tense fight scene, which is rare – once again the star of this episode was Will Tudor’s Sebastian, or Jonathan as we know him now, as he recounted the sad and terrible story of life growing up as Valentine’s demon child.

His darkly compelling storyline worked wonders in fleshing out an already interesting character with this new information, and also managed to give Valentine’s somewhat old (and significantly underused so far this season) character a new nefarious purpose too. This episode did include a couple of odd beats – Robert Lightwood’s return was another random one without much weight and brought with it a revelation that could have easily come from someone else – but by the end of it the lines of good and evil are clearly drawn, with Clary and Jace’s angel blood providing a stark point of contrast to Jonathan’s scorched, demonic presence.Which leads us swiftly onto a ‘A Dark Reflection’, which marks the start of high-stakes storyline that will see us through to the end of the season. There is a lot at play here, from Max Lightwood’s being approved for Shadowhunter field work to the secrets Alec is keeping from Magnus threatening to drive them apart, but mostly this episode centred on two groups’ search for the Mortal Mirror, the final Mortal Instrument and the one thing that’s currently stopping Valentine and Jonathan from being able to raise the angel Raziel and have him grant them their wish – which for Valentine would be destroying the Downworld once and for all, but Jonathan’s demon blood may mean he has another idea in mind.

And really, it’s Jonathan’s unpredictability that’s selling a lot of the tension in Shadowhunters at the moment. Despite his character’s shifting into a volatile one with an intense fascination with his sister Clary a bit too quickly and without a lot of reasoning, it’s brilliant to watch and actually gives Katherine McNamara a more interesting partner for Clary to work off than Jace’s agreeable enabler. Clary’s fighting for her brother and arguing that he needs to be given a second chance is the most we’ve seen her clash with Jace since the series started and Jace’s own stance also puts him at odds with Jonathan too – and considering both of them want Clary in one way or another, it’s setting up another very interesting dynamic for the episodes to come.It was a little disappointing to see Simon’s own arc take the backseat we knew was coming, and more annoying than not that Maia tried to distance herself from the thought of a relationship with Simon despite it being one of her more consistent character traits in previous episodes, but it’s also no surprise that Shadowhunters doesn’t follow the side plots as closely as the main one. So it’s a small mercy that the main plot right now is so gripping. With Clary and Jace’s relationship currently being tested by things that aren’t about their maybe being related, and Jonathan’s twisted definition of love delivering more instability into his and Clary’s already-complicated relationship, the plotted action may have a long way to go to catch up to the emotional stakes, but ‘A Dark Reflection’ has definitely hinted at some great things to come.

As ever with Shadowhunters, these last three episodes have been a mixed bag of good plot, bad plot and character quirks that are neither here nor there, but watching them in quick succession has meant that some of the less forgivable aspects of the series haven’t seemed so bad when the more exciting parts are waiting just beyond the next episode button. Reducing its reliance on the book series as a source has only done good things to this show as it worries less about fan-pandering and more about plot and structure in its own right, but above all else this season has greatly benefitted from the arrival of one Jonathan Morgenstern, and I’m looking forward to seeing how much more trouble he’ll cause next.

‘A Problem of Memory’ ★★★

‘Day of Atonement’ ★★★

‘A Dark Reflection’ ★★★