Episode 50 of The Trigan Empire
The Heat Controller
aka Het kasteel in de bergen (Dutch title)
The Castle in the Mountains (Dutch title, translated)
The Heat Controller was originally published in 8 installments in issues 682 (8 February 1975) to 689 (29 March 1975) of Look and Learn magazine.
To date it has not been reprinted in English.
Plot summary (Dutch)