Yes, this is the second of three stories where Doctor Who went abroad on-location, and this time it's Amsterdam. Two Australian students on holiday, Colin Frazer and Robin Stewart, spend the night in an abandoned crypt near a fountain, and before long, Colin vanishes, only to turn up a zombie under control of aliens, leaving Robin in a lurch. His only hope is to get help from Colin's cousin, scheduled to arrive at Schiphol Airport.
For the Doctor and Nyssa, they pass near an area in space that was called the Arc of Infinity because it's the gateway between the universes of matter and anti-matter. The Doctor is attacked by a strange alien, initially billed as the Renegade, but then things get worse. It's another return to Gallifrey, only this time, the Doctor is in danger of suffering the same fate as Morbius, (q.v. The Brain of Morbius). An alien from the realm of anti-matter has been partially successful in bonding with the Doctor to get his polarity reversed. However, for that to happen, someone had to have given this alien the Doctor's bio-data extract, and only members of the High Council of Timelords have that power. The Timelords, still led by President Borusa, don't have time for that--they prefer the Doctor's execution to retain control of the Space-Time Matrix and prevent billions from being killed.
The Doctor has a few allies, such as Damon, a Gallifreyan technician who was on duty when the Doctor's bio-data was being accessed. There's also his old instructor Councillor Hedin of the High Council, a kindly person who manages to get Damon and Nyssa to visit the Doctor even though the Doctor is denied visitors under orders from the meticulous Castellan and his lackey, an unpleasant and trigger-happy commander named Maxil. However, Episode 2 ends with the Doctor apparently being terminated. What then?
There's a lot more to Nyssa that comes out here. Apart from her sensitivity, she gets to shoot some guards in the story, all in aid to rescue the Doctor. After all, the Doctor is all she has since the murder of her parents and destruction of her planet. One of Sarah Sutton's best moments in the series.
The Renegade and his pterodactyl-like helper have interesting H.R. Giger-influenced designs. However, the on-location shooting is utilized quite well so the viewer sees quite a lot of the streets of Amsterdam, particularly in a climactic chase scene in the last episode, where the Doctor and his companions are chasing the decaying Renegade (also played by Peter Davison, who must've made quite an impression running down the streets with a mixture of green-dyed glued Rice Crispies on his hands and face).
Other performers: Elspet Gray (Thalia) also appeared in the first Black Adder series as the Queen. Colin Baker (Commander Maxil) makes his first appearance in the series, and it's ironic that he shoots the Doctor in Episode 1, because at the end of next season, Baker succeeds Peter Davison as the Doctor. Also interesting is that he was a candidate to play the Castellan, but lost out to Paul Jerricho, who also beat out Patrick Stewart. But guess who else was initially considered for Maxil? Pierce Brosnan!! I kid you not! And Hedin is played by Michael Gough (Bruce Wayne's butler Alfred in the Batman movies).
The 20th season was the most memorable season for me, because I was really starting to get into the series, and Arc of Infinity really stayed with me, because it was a Time Lord story, the scenes in Amsterdam, and Sarah Sutton's appealing performance. Enjoying this story does not require smoking cheap grass from Amsterdam.