Continuity is important with any form of storytelling. It's one of those things you notice when its wrong, cheer when its right and complain when it's not even there. Nightvisiting falls into the 'cheer' category. It would have been easy for this episode to ignore what came before it given that it focuses largely on a character we hadn't seen before (Tanya's (Vivian Oparah) late father) but instead the episode awards the viewers for paying attention by bringing back someone whom we had rarely seen before she met her demisei n the first episode: Ram's (Fady Elsayad) girlfriend Rachel (Anna Shaffer).

Nightvisiting opens with a montage of Tanya and family, explaining how she lost her father Jasper (Kobna Holdbrook-Smith) to a stroke. Two years later, on the anniversary of his death, Tanya retires to bed - to find her father sat in the far corner of the room. All over London, people are being visited during the night by deceased loved ones. But why are the dead returning from beyond the grave? And what do they really want from the people they visit?

It's nice to see Class continue the trend of each episode focusing on one of the members of the Coal Hill gang. This week's is largely Tanya's story and how the death of her father has affected her two years' on. We may get to see Ram encounter his dead girlfriend and Miss Quill visited by her deceased sister but they are merely sub-plots to the narrative of Tanya's grief. We only meet Jasper for the first time in this episode but thanks to the genius montage at the beginning it feels like we've known him since the beginning of the series. The montage really makes us care for Tanya's relationship with her father; in just three minutes we get a sense of just how much he meant to her and the fact that he was cruelly taken away from his daughter so soon into her life highlights how tragic their story is. This helps to make the situation of Tanya meeting her father even more desperate, to the point where you really don't know if she will let 'Jasper' (spoilers, he isn't really her father) take her away with him. Deep down it is perhaps a metaphor for dealing with grief and learning to move on - something that all of us who have lost someone can relate to. For instance, I lost my Grandad in 2007 and I remember how hard it was to cope with the loss of the man who inspired my passion for movies (he used to work as a projectionist at the Hollywood Plaza in Scarborough). I had to move on though, just as Tanya must learn to from the passing of her Dad.

Talking of Tanya, Vivian Oparah does a very impressive job in the role. She gives an extremely powerful performance that is certain to make you cry (unless you're Donald Trump, of course). It is one of the best performances in any of the Doctor Who spinoffs, even rivalling Daniel Anthony as a homeless Clyde in The Curse of Clyde Langer. Vivian Oparah is probably the strongest actor of the four leads; I have a feeling as with Tommy Knight that she'll go onto bigger things once Class is over.

The other highlight of this episode is the Lankins, a very creative threat who take on the form of deceased loved ones to lure the living. The idea could be considered a morbid take on the Sirens from Greek mythology: beautiful mermaids who were believed to attract sailors with enchanting music to shipwreck. The episodes' use of the Lankins places an interesting spin on the idea of heaven; the idea that heaven and hell are one and the same and also the idea that it's just sentimental stuff the 'pathetic humans' fall for. It is a view that's likely to offend a significant proportion of viewers but is a fresh take on the concept than the ideas often thrown about regarding life after death.

There is a major problem with this episode however. In the episode we are told Charlie (Greg Austin) sees a glimpse of his family during his sex with boyfriend Matteusz (Jordan Renzo), however it is never explained why it's only a 'glimpse' and not a full-blown appearance as with the rest of the Lankin's deceased. Is it because love is different in his world (as he states in the episode)? Or is it because (again, as the episode itself dictates) he hated his family for only caring about his image as prince and not respecting the fact that he's gay? Either explanations would have sufficed for why it is merely a glimpse; this is an issue that I feel would have been easy for Patrick Ness to fix.

Overall, Nightvisiting is a hugely emotional episode about the story of Tanya and her deceased father. It poses interesting questions on heaven and hell. Vivian Oparah is outstanding at portraying Tanya's grief, even managing to make us question whether she will fall for the Lankin's trap (even though we know she's one of the four leads). It's great the way the episode sticks with continuity also, by bringing back Ram's dead girlfriend Rachel. The only real disappointment is the half-baked idea of Charlie only seeing a glimpse of his family. It's never explained why Charlie's is only a glimpse, something that could have been easily fixed with a line or two.