The two adventures on the tape are *very* different. They were obviously created independently and then brought together under the crude "Merlock" framing device.
In fact, The Deeds of Glengarry Hall is actually an updated and slightly reworked version of Andy Hackett's earlier adventure, To the Manor Bourne. The "Merlock" version features slightly tweaked puzzles (such as the substitution of the "red herring") and an improved engine/graphics; but the solution is otherwise identical.
The eight adventures of Merlock the Mede were planned to be delivered across a "tetrad" of releases. Players were promised a free Merlock digital watch, if they collected all four cassettes. However, only the first compilation was released. The planned Amstrad version, mentioned in C&VG January 1986 also doesn't seem to have happened.
[+] Users who have solved this game
[+] Users currently playing this game
This game was already dated when it came out: too slow and simple, despite it being an upgrade of "To the Manor Bourne".