Episode 39 of The Trigan Empire
The House of the Five Moons
aka De dubbelganger (Dutch title)
The Look-alike (Dutch title, translated)
The House of the Five Moons was originally published in 9 installments in issues 597 (23 June 1973) to 605 (18 August 1973) of Look and Learn magazine.
It is reprinted in the Don Lawrence Collection Volume 10, The House of the Five Moons.