Dear Detective

 is a quest in Fallout 4.

Quick walkthrough

 * 1) Enter Fens street sewer.
 * 2) Find the 4 tapes and listen to them :
 * 3) Dear detective 1 - Right as coming down the ladder from the street.
 * 4) Dear detective 2 - On a barbecue next to a skull.
 * 5) Dear detective 3 - On a table next to a green/yellow chair in a room with a mannequin, candles, and various crates.
 * 6) Dear detective 4 - Near the end of the tunnels, in an alcove with a safe behind a chain fence.
 * 7) Find the bodies of the detective and the serial killer.