Here is the full list of all 15 Lord Winklebottom Investigates achievements.
Eat the plant in front of Pumphrey.
Made tea using milk first.
Complete the game without asking for Frumple's advice.
Finished the game.
Reached the epilogue.
Reached act 3.
Successfully fake a seance.
Find motives for every character.
Reached act 2.
Have Frumple perform an autopsy.
Read all about Inspector Waffles.
Reached act 1.
Get Salty Walters out of the pub.
Picked up all the litter.
Made tea using tea first.