Following a Lead Walkthrough guide

You were a pawn all along! Follow your only lead to redeem yourself to your Dark Brotherhood family.

Completing "A Kiss Before Dying" will immediately start this quest.

・Go to Anvil and and wait near the barrel behind the statue in the pond.
・Confront Enilroth about the fake Dead Drop Orders.
・Head to the Anvil Lighthouse and get the Cellar Key from Ulfgar Fog-Eye.
・Continue your investigation inside the Anvil Lighthouse Cellar.
・Read the Traitor's Diary.
・Meet up with Lucien at the Applewatch Farmhouse.

・To get the Gold reward from the last quest, you can try stealing it from Enilroth.
・If you want a hint about the real traitor, grab the Mother's Head from the cellar and drop it at the Applewatch Farmhouse. When you talk to one of the members there, their dialogue will be different.