THE RAILROAD QUEST 08 - Burning Cover
Triggered by making the Institute hostile to you before completing The Railroad Quest 05 - Underground Undercover
Note: This is not a required quest. It is instead a way for you to transfer between questlines (from The Railroad to Minutemen) if you screw things up. Triggering this quest locks you from completing The Railroad questline. This can be triggered by killing friendly Institute personnel or by performing other actions that the Institute dislikes.
Objective: Report to Desdemona
After blowing your cover with the institute, Desdemona will tell you that the infiltration plan will no longer work. She'll suggest you work with the Minutemen instead (Minutemen Quest 05 - Inside Job) by using the network data you obtained when you first arrived at the Institute as another potential way to breach the Institute's facility.
Objective: Talk to Preston
Depending on your faction progress, you will either need to join the Minutemen (by completing Minutemen Quest 01 - When Freedom Calls) or just hand over the holotape to Preston if you're already a member. This will ally you with the Minutemen faction questline to complete the game.