It’s difficult to know how to evaluate this episode- whether as an episode in its own right, the second half of the two-parter, one of the turning points of the season or in the context of the whole of Buffy and Angel. Because this is one of those episodes which affects all those contexts. There are ideas here which would still be cropping up years later in Angel- and if there’s a resolution to the plot threads started up in the previous episode, it serves only to push the narrative and characters further on. And if there are weaknesses in the way the immediate situation is handled, the long-term effect on the Buffyverse is nothing short of defining.

To begin with the immediate situation: at the end of ‘Surprise’, Buffy and Angel do the naughty, and in the middle of the night Angel wakes in agony, collapsing in the street. One of the strengths of this episode is the way it manages to deal with the issue of the loss of virginity and first sexual experience, and yet repeatedly understates the point. Words such as "virginity" and "sex" are avoided, and it’s left to Willow’s intuition and deductive skills to work out why Buffy takes Angel’s change of personality so personally. This is, of course, one of those Buffy episodes which uses the fantasy/horror elements of the show as a metaphor for life experience- in this case, "I slept with my boyfriend and he turned nasty"- but what’s striking is that what happens between Buffy and Angel affects everybody. I believe I’m right in thinking that this is the point where the Christian Right in America, who’d reluctantly reached an accommodation with the show as a battle of good and evil, switched off in disgust, but the message is a responsible one. Sex has consequences, and those consequences can affect a lot of people. An interesting counterpoint is the similar emotional impact of Willow finding Xander and Cordelia in a clinch- while it isn’t the moment when they accept that they’ll never be together, Alyson Hannigan is once again so damn good at conveying Willow’s maelstrom of emotion faced with Xander’s apparent betrayal of their friendship that there’s a truth to her performance and the fact that she puts the issue behind her to work together on the problem at hand. Real people behave like that.

‘Innocence’ is also, of course, the point at which the season starts to turn for home. Central to this is the introduction of Angelus- in one sense, the embodiment of everything Buffy fears about giving herself sexually to Angel, and in another the shadow which continues to haunt Angel. The very fact that five years later the character was brought back temporarily in Angel only goes to show how potent the concept of the character is. On another level, it’s refreshing to see David Boreanaz given something else to do apart from looking dark and moody; Angelus gives him the opportunity to flex his acting muscles a little more and play a different character. The scenes where Angelus uses his knowledge of Buffy’s insecurities to taunt her with her worst anxieties about sleeping with Angel are agonising to watch; he knows Buffy’s buttons well enough to reduce her to tears at the thought that her performance was to blame for his change in personality. It’s the ultimate twist in the show’s line-up, and it gives the season fresh impetus as its last third comes into view.

And the long-term effect of this episode’s events is immense as well. There are the first signs that Willow and Xander are going in different directions; although Willow is devastated to find that Xander seems to prefer canoodling with their mutual enemy Cordelia to being with her, she’s also getting closer to Oz, who typically pins down within ten seconds the reason why she wants them to make out in the van while waiting for Xander and Cordelia to steal the missile launcher. The presence of Angelus begins the process which would ultimately end at the culmination of the following season, as Buffy and Angel ultimately realise that they can’t ever be a couple. It’s another step on Buffy’s road to maturity, too- catching a later episode on Sky earlier on this evening, Sarah Michelle Gellar really manages to find the vulnerability and inexperience in the teenage Buffy which gets knocked out by another five years of slayage; it’s all the more powerful when we can see exactly how beautiful Sarah Michelle Gellar is, and that a character that good-looking can have these insecurities.

And yet, ‘Innocence’ is strangely unsatisfying. It’s as if its billing as an ‘event’ episode overwhelmed the need to tell a coherent story. Although I admit that I didn’t really notice it, Keith Topping’s guide points out that there are major timing discrepancies, and having built up the Judge as a new villain, he’s dispatched in a summary fashion- I didn’t know that missiles weren’t "forged", but apparently they aren’t. It’s a fine distinction which looked a bit ropey when Shakespeare used it in Macbeth, and it feels awkward here. So, in the final count, as a crossroads in the ongoing story of Sunnydale, ‘Innocence’ is massively important- it’s just a shame they forgot to tack on a proper story as well.