The Lost Patrol

The Lost Patrol is a quest in Fallout 4.

Quick walkthrough

 * 1) Investigate the battle site north of Relay Tower 0MC-810.
 * 2) Follow the radio distress signal.
 * 3) Listen to the Battlefield holotape.
 * 4) Investigate the National Guard training yard.
 * 5) Follow the radio distress signal.
 * 6) Listen to Knight Astlin's holotape.
 * 7) Investigate the Revere satellite array.
 * 8) Follow the radio distress signal.
 * 9) Listen to Scribe Faris' holotape.
 * 10) Follow the radio distress signal.
 * 11) Investigate Recon Bunker Theta.
 * 12) Speak to OR kill Paladin Brandis, depending on relation to the Brotherhood (ally/enemy).
 * 13) If Paladin Brandis is spoken to: Report to Danse.
 * 14) If Paladin Brandis is killed, the quest is marked as completed.
 * Speak to Brandis when he returns to The Prydwen for his thanks and a reward from him, his personal gun Survivor's Special

Detailed walkthrough
The player character will detect a distress signal once they are near any one of the three locations where Brotherhood of Steel followers perished. To complete the objective, the player must loot holotapes from the fallen soldiers, then play them from their Pip-Boy.

Knight Varham's holotape is located in a ruined house north of Relay Tower 0MC-810, south of Greentop Nursery and east of Taffington boathouse.

Knight Astlin can be found behind a table in the recruitment office at the National Guard training yard.

Scribe Faris is found at the Revere satellite array. He is in a metal and wood structure connected to the southeast array tower. This area is inhabited by super mutants.

Once all three holotapes have been played, a quest marker will appear at Recon Bunker Theta which is otherwise inaccessible. Once there, one will be accosted by Paladin Brandis who will demand to know why the Sole Survivor is there. If the player character tells him the fate of the soldiers, he will allow the Sole Survivor to loot the items in his home, which includes a fusion core.

The Sole Survivor has the option of persuading him to rejoin the Brotherhood of Steel. They must pass three conversation checks and if any of them fail, he will remain where he is. If successful, they will find him aboard the The Prydwen where he will reward them with the Survivor's Special.

Bugs

 * If the player character puts off completing this quest until after Paladin Danse has become a potential companion, they may be unable to turn the quest in as he will only offer companion dialogue options. However, after a period of time the mission turn in point will be transferred to Captain Kells, allowing for completion.
 * Captain Kells will give generic dialogue instead of allowing the player character to turn in the quest until after they've completed Show No Mercy for the Brotherhood of Steel.
 * Speaking to Brandis (or simply entering the National Guard training yard) may cause the player character to lose Fast Travel capability. Every time the map is opened, the same message will appear: "Fast Travel is currently unavailable from this location." This message appears anywhere, even if there are no enemies around, the player character is not overencumbered, and are not in a building.
 * If Brandis is spoken to before starting the first Brotherhood Quest (Fire Support), the quest will not require to return to Danse; it will simply be marked complete.
 * Failing to complete all speech challenges, but still convince Brandis to join the Brotherhood of Steel would still prompt to Paladin Danse. Killing Brandis will give the unique weapon, but still allow for the Sole Survivor to turn in the quest to Paladin Danse for a double reward.
 * If you have completed the quest Blind Betrayal before finishing the Lost Patrol quest, and have kept Paladin Danse alive as your follower; then upon completing all speech challenges to convince Brandis to join (with success) he will start attacking you and Danse. As long as you dismiss Paladin Danse and are not an enemy of the Bos; then he will not attack you or Danse. You will then be able to complete the quest as usual.