Distress signal (Relay tower 1DL-109)

Distress Signal is a quest in Fallout 4.

Quick walkthrough
Found when extending the Relay Tower 1DL-109. Woman says she is hiding in train car with "Thomas." Shortly into recording she describes her hiding spot as a train car.

Detailed walkthrough
Follow railline south and you will find a train with several feral ghouls, including a legendary. Crouch near overturned blue train to enter train and find skelton remains of woman in recording,