This achievement can be earned in mission 5. Once you get into the museum, you'll find a large open room with multiple levels of balconies and witches patrolling at various points. On the balcony on the second floor is a large device with glowing paint around it. Once you've eliminated the witches (otherwise they'll attack when you start), pull the lever on the side of the device. This will play the first "echo" which is a memory of a conversation from the Sisters of the Oracular Order. Repeat this two more times to unlock the achievement.