You know, the one with the big battles. No, the really big battles. Actually, although the battles are the one thing that everyone remembers Sacrifice of Angels for, that is actually doing the episode an injustice. It marks the turning point for Dukat, who descends into madness after this episode, and the re-introduction of the Prophets, who would become increasingly important to the series from this point on.

Odo has to decide who his friends are, Damar decides who his enemies are, and Weyoun is just having the time of his lives. It's crunch time for everyone, (esp-ecially if you're the 'angel' to which the title refers) but the war itself is only just hotting up. One of the show's very finest instalments. (TS)

Although apparently based on the 1970s BBC series of the same name, which concerned a government-run investigative team who uncovered threats to world ecology, this one-off special is the same programme in name alone. And even then, they've added a space.

A very expensive-looking production, this film updates the concept to the Nineties where former head of Doom Watch, Dr Spencer Quist gathers together a rag bag team of students and professors with an interest in ecology in order to find out what's been happening in a remote power station near Newcastle.

With some fine performances and excellent (if sometimes gory) special effects, the production is only let down by its occasional impenetrability - the writer should have been told that not everyone has a degree in advanced scientific gobbledegook.

On the basis of this film, Doom Watch is certainly deserving of a follow-up series, if only because beautifully-produced Sci-Fi drama like this is such a rarity on British TV. (CH)

The sliders arrive in the middle of the ocean. This causes some degree of concern, as swimming to shore after each slide may not be useful or possible. Bumped out of their 'sliding radius', the team seek passage on a ship to get back to dry land. Then it gets boarded by pirates. Don't you just hate it when that happens?

Possibly one of the dafter ideas the Sliders creators have had, Heavy Metal is actually one of the more enjoyable episodes this season, if only because it's something a bit different. Plenty of fighting, a spot of action, sympathetic characters… and Maggie manages to get lucky in a surprisingly hot and heavy scene. And you can't say fairer than that. (PS)

Season Four's Holly story is an undoubted highlight of the show's entire run, as the crew discover a white hole, spewing Time back into the universe in random pockets.

So what is it? Well, attempts to boost Holly's IQ back to 6,000 so she can count without banging her head on the screen result in her lifespan being reduced and the Dwarf floating in Space.

So what is it? Only joking. Season Four contains some of the best Sci-Fi concepts the show has utilized, and playing pool with planets is fantastic.

So what is it? I believe we've experienced this Time period before. Well, attempts to boost Holly's IQ... And that one. Luckily, the comedy isn't lost in the shuffle with Rimmer's attempts to explain a simple concept to Holly and the return of Talkie Toaster particular highlights. So what is it? Well, attempts... (PS)

As a pedantic Doctor Who fan, it is my duty to point out that Mawdryn Undead completely messes up all established UNIT continuity, by setting part of the story in 1977. However, once one gets over that small point, the story remains one of the highlights of the Davison era.

As well as bringing back the wonderful Nicholas Courtney as two versions of the Brigadier, we also meet new companion Turlough, who is actually plotting to kill the Doctor for the Black Guardian. And this is only the sub-plot! The main story revolves around a group of scientists who wish to gain the secret of eternal life, but entirely mess it up. David Collings excels as the tortured Mawdryn while Davison is just hitting his peak. An adventure which showcases Doctor Who at its most thoughtful and scientific. (TS)

This is an introspective Stargate tale that sees most of the main cast discovering a secret (surprising eh?), Daniel's about Sha're and Carter's about her father.

Jackson's return to Abydos is the most affecting of the plotlines, but Carter's reunion with her father is also emotionally played. Meanwhile, O'Neill meets a reporter who has somehow uncovered the truth of the Stargate Project and is determined to expose it. Truth exposing is unusual for The X-Files' Chris Owens, but he does a fine job with a small role here. (PS)