- Give Carrington his prototype
- Retrieve the dead drop
- Meet Old Man Stockton
- Secure the rendezvous point
- Wait until nighttime for Old Man Stockton
- Wait for Railroad contact
- Follow High Rise
- Talk with High Rise
- Report back to Doctor Carrington
Speak to Doctor Carrington after you have completed The Railroad essential Quest Tradecraft. He will ask you to assist H2-22 at Bunker Hill. Head east of Monsignor Plaza in the Cambridge neighborhood to get to the dead drop in the mailbox. Mind the Mirelurk horde in the area. Remove Stockton's Holotape and listen to it. You're to travel to Bunker Hill to speak with Old Man Stockton, using the countersign to maintain secrecy.
Head to the church maked on the map, eliminating any and all threats along the way. Once inside the church, sit on one of the pews and wait until 11:00 PM. Stockton and the synth will show up. Have a conversation with them and then wait for High Rise to arrive. He asks you to help him. Travel south to Monsignor Plaza, and clear the area completely of foes and continue on to Ticonderoga Safehouse. Check in with Carrington for your reward of caps, Bobby Pin 5x and a random weapon.