I'm not sure why the ratings for 'Substitute' are relatively low compared to other Waking The Dead episodes. I'm a big fan of the series. Enjoyed it first time around and am enjoying going through the series again. Obviously there a some episodes that are better others - although that is obviously in the eyes and ears of the beholder and even as a fan I can understand why WTD didn't have the same impact when it got to it's 8th series. We do get used to the formula and therefore have more a clue to where the narrative is going by the 70th or 80th episode than we did in the first couple of series. Yet, the writing, acting and directing still had the ability to keep you on the edge of your seat. Substitute is one of those. There are truly shocking moments (one in particular) and some uncomfortable scenes. It is slightly different from other WTD episodes because it is one of the few stories that mainly features just two of the team. This episode really only needs Boyd and Eve. The others are on the periphery and don't really need to be there. Happily Trevor Eve and Tara Fitzgerald totally own their parts as do the guest actors. Perhaps, the story is a bit unreal but that doesn't stop it from being thrilling entertainment and does open the debate to the main issues of the story. This like many, many, WTD episodes would have made a very good cinema release film.