At the start of Dangerous Journey there’s no real reason why the Doctor and his friends don’t return to the TARDIS and leave. Although they were concerned about Farrow’s dead body in the previous episode, the Doctor accepted that given their current size there’s nothing they can do to help. But the arrival of Forester and Smithers panics them and Ian and Barbara run straight into Farrow’s briefcase (another nicely designed prop). They could have hardly picked a worse place to hide in as it’s then taken into the house.

Smithers might be a blinkered scientist, but he’s not a a complete fool. He quickly ridicules Forester’s claim that Farrow was killed in self defence, pointing out that the unfortunate man was shot through the heart at point blank range. Smithers, unlike Forester, isn’t interested in profit – he’s motivated purely from a desire to save lives. “I’ve seen more death than you could imagine. People dying of starvation all over the world. What do you think I started on research for?”

But whilst he may have the best of intentions, he’s blinded to the issues with his formula. The misguided scientist would be a character who would feature numerous times in subsequent Doctor Who stories. Normally the Doctor would have a scene where he could explain to him or her the error of their ways. But due to the Doctor’s small stature this can’t be done here, so Smithers remains unenlightened until he reads Farrow’s notes in the next episode and finally understands just how flawed his work is.

One thing that’s always slightly irritated me about the story is the moment when Barbara touches some seeds which are coated with DN6. She mentions this in passing to Ian (who ignores her) but when she realises that she’s been infected, why doesn’t she tell Ian? Ian doesn’t come out of this very well either as he’s shown to be, once again, rather slow on the uptake.

But although the story isn’t quite gelling you can always just sit back and enjoy the visuals. The sink, complete with plug and plughole, is yet another wonderfully designed Raymond Cusick set and the animated fly is also stunning. Doctor Who had its fair share of design disasters (the paper-plate Dalek flying saucers in the very next story, say) but when things work they really work.

There’s a faint touch of the series’ original educational remit as the Doctor tells Susan that since they’re in the sink their voices will be magnified. Ian also explains why communication with the people in the house would be impossible. “Imagine a record played at the wrong speed. We’d sound like a little squeak to them and they’d sound like a low growl to us”.

The cliffhanger is a decent one – the Doctor and Susan shelter in the sink’s pipe as Smithers washes his hands. That such a mundane action could be fatal – they risk being swept away by the deluge of water – is one of the main strengths of the story.