one visible thing. Understand "follow [any person]" as following. Understand the commands "chase" and "pursue" as "follow".
Check following:
if the noun is the player, say "Wherever you go, there you are." instead;
if the noun is visible, say "[The noun] is right here." instead;
if the last location of the noun is not the location, say "It's not clear where [the noun] has gone." instead.
Carry out following:
let the goal be the destination of the noun;
if the goal is not a room, say "[The noun] isn't going anywhere you can follow." instead;
say "[Noun] heads out. You follow him through the school, finally ending up at [goal].";
now the noun is in the goal;
now the player is in the goal;
if the goal is room 10:
now door to room 10 is unlocked;
now door to room 10 is open.
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Volume 3 - The Player