Hi Gavinom!
You get poisoned at the end of the tunnel, just before reaching the Queen's chamber. In order to achieve that Archie must be doomed so make sure to do at least five points out of these:
1- be a jerk when he repairs the elevator (1 point)
2- poking a finger in the eye of the skeleton in the 'dining' room, the one on the floor (1 point)
3- pull the lever on the right in the infirmary, the one that makes stones fall on you (1 point)
4- when you inspect the bed frames in the infirmary, have Archie inspect the ones with the wasps (1 point for each bed, up to 4 points)
5- these are in the hideout: tell you like pineapple on pizza & "you don't get it" when speaking about friends and bullies (2 points)