With Marco and the others lacking enough water to make the journey to the oasis, it falls to the Doctor to save the day. He notices that moisture has formed on the inside of the TARDIS overnight and saves every last drop. We then have another quick science lesson as the concept is explained to Marco (and the viewers at home).

IAN: Marco, you remember, last night it was cold. Bitterly cold, Marco. The outside of the caravan cooled, but the inside stayed warm, and so moisture formed on the inside. It’s condensation, we just call it that. It’s just a name.
SUSAN: That’s true, Messer Marco. It was running down the walls, and from the ceiling. We, we took it in this, look, we squeezed it in here. You see?

These precious drops of water are enough to aid their journey to the oasis, where they find Tegana. He tells them he was unable to travel back with water as the oasis was surrounded by bandits during the night. As so often in the early stories it’s not the Doctor who exposes the fallacies in his statement (if bandits were there, why didn’t they light a fire since it was a cold night?) but one of the others – in this case Barbara. Her suspicions against Tegana only harden as the episode continues, culminating in her capture when she ventures into the Cave of Five Hundred Eyes.

One noteworthy aspect of these early scenes is that Tristram Cary’s music has an electronic feel (similar to his score for The Daleks). This fits the mood well as Marco and the others face death under the unforgiving sun. Once they are rescued, it changes back to traditional instruments (as it is for the majority of the story). It’s a pity that Marco Polo is the only of his Doctor Who scores not to exist, although we should be grateful that his other music does.

Having reached the Tun-Huang Way Station, Marco mentions the nearby Cave of Five Hundred Eyes, a place once frequented by the Hashashins. Although Ping-Cho has never heard of the cave, she does know a story about Hulagu and the Hashashins and promises to tell it to them later. This is an extraordinary sequence – the story stops for several minutes for a spot of local colour. Like the chat about condensation, it’s probable to view its insertion as another educational box-ticking exercise. But it’s charmingly performed by Zienia Merton, who delivers the lengthy monologue with aplomb. It’s easy to imagine that the air would have turned blue had it been given to William Hartnell!

Gracious maidens, gentle lords, pray attend me while I tell my tale of Alaeddin, the Old Man of the Mountains, who by devious schemes, evil designs and foul murders ruled the land.

No host of arms, no vast array of banners served this wicked lord. They were but few, ruthless, reckless men who obeyed his cruel commands.

Thus did he persuade them. Promising paradise, he gave his followers a potent draught and whilst they slept transported them to a vale where streams of milk and honey, wine and water, flowed.

Here were gardens and flowers of every hue and essence. Here, too Golden pavilions outshone the sun and even the stars of heaven envied the bejewelled interiors strewn with incomparable silks, tapestries, and treasures.

Hand-maidens, dulcet-voiced, soft of face, attended them, and thus bemused did they dwell in this man-made paradise until Alaeddin intent upon some evil deed, proffered again the hashish draught and brought them sleeping to his castle.

“What lord, are we cast out of paradise?” awakening, they cried.

“Not so. Go abroad, seek out my enemies and strike them down. But care not for your lives. Paradise is eternal.”

So terror stalked the land for many years. Then one day, came mighty Hulagu to stand before Alaeddin’s lair for three long years in siege. Thus fell Alaeddin and his men.

Now honest hands reap harvests of life from the soil where death and evil reigned. And those who journey through the vale are heard to say ’tis truly paradise today.

When Barbara notices Tegana leave the room after Ping-Cho’s tale, she follows him as he heads up to the Cave of Five Hundred Eyes. She doesn’t hear Tegana plot Marco’s destruction and the theft of the TARDIS, but finds herself captured by a group of Mongols who hold her in the cave whilst they play dice. In the next episode she tells Ian that they were playing dice to decide which of them would kill her, but it’s no stretch to imagine that they were also keeping her alive so that they could take turns to rape her. Otherwise it would have made more sense to quickly kill her and leave. Barbara becomes the object of male interest several times – in the very next story The Keys of Marinus and also during season two. Sometimes played for comic effect (The Romans) and other times played dead straight (The Crusade).

An intriguing part of the episode revolves around Tegana’s attempts to sow discord between Marco and the TARDIS crew. Why is Tegana doing this? He clearly doesn’t have Marco’s interests at heart, since he plans to kill him very soon, so is it possible that he fears the Doctor’s magic? Or it could be that he simply enjoys stirring up trouble amongst his enemies?