This review WILL CONTAIN SPOILERS for the episode to be discussed, if you do not want certain plot points or story spoilt, please do not read further.
It would finally look like Arrow has decided to deal with it's Malcolm Merlyn problem. After a shaky third season a lot of fans were looking forward to Arrow addressing a lot of the left over story lines from last year and putting some of them to bed, 'Sins of the Father' finally did just that.
The Arrow team aren't the focus of this weeks episode, despite it being about trying to save Thea's life, instead time is given over to finally resolving the Nyssa/Merlyn story, and the series definitely benefits from doing this.
One of my biggest issues with the last year and a half of stories from Arrow has been Merlyn, and his almost honorary membership to team Arrow. In the comics Merlyn is Oliver's arch rival, his general Zod, Sabretooth or Sinestro. He's supposed to be the evil version of what our hero is, so having him playing nice with Oliver and the team this last season has not only felt wasteful of the character, but kind of goes against what he's supposed to be about.
So when Merlyn agrees to give up being Ra's in order to save Thea I thought the new status quo would be carrying on, imagine how delighted I was when he turned around and betrayed everyone by not wanting to give up power, even to save his daughter. Now this is the Malcolm Merlyn the show has been missing.
What ensues is an all out ninja assassin war on the streets of Star City, which is always cool to watch. It's nice to see that despite trying to play peacemaker when push comes to shove Oliver and the team side with Nyssa. Even if you forget that Malcolm killed Tommy, brainwashed Thea into killing Sarah and engineered all of the events of season three he wasn't going to get Team Arrow on his side. During her time on the show Nyssa has shown that despite being an assassin and the daughter of Ra's she's a much better person, that she has love, compassion and forgiveness inside of her, and that's the much better candidate to be leading the league.
The episode is also good at showing how much Oliver has grown over the course of the series, when instead of killing Merlyn in single combat he simply cuts his hand off. The Oliver of season one would have killed him without a single thought, even before you take into consideration all that Merlyn's done to our team. It's clearly a move that the writers took because they don't want to lose Barrowman from the series, but it's also a good character moment for Oliver, though one I'm 100% certain he will regret before season four is finished.
Elsewhere in the episode Felicity deals with her own father issues as she comes face to face with the man who abandoned her and her mother years before. Whilst some might find this second story a lot less interesting than the ninja assassin war it actually works very well in an episode all about fathers, and never goes and steps on the toes of the main plot.
Wanting desperately to believe that her father could be the good man he claims Felicity is heartbroken to learn that everything her mother ever said about the man is true and that he can't be trusted. Discovering that he's only using Felicity to try and steal from Palmer Tech she does the only thing she feels is right and turns him over to the police to be arrested.
'Sins of the Father' is a cleanup episode where some of the outstanding plot threads are finally (hopefully) put to bed. The only way that the main season arc is effected is by Merlyn becoming a clear villain again for the first time since season one (yes, it's been that long!) and joining up with Damian Darhk. Merlyn gives Darhk information about Oliver's son, William, which just adds to the who's in the grave/who does Felicity want Oliver to kill questions that have been driving fans mad for months.
Wherever the show goes from here things are sure to get worse for our heroes as Merlyn joins forces with Darhk and Hive.