This achievement is earned for finding optional photo #10. If missed on the first run, you can "Play Episodes" and select specific parts of the Episode in order to find the missing optional photos through collectibles mode. The following collectible is described and can be seen below:
] - Optional Photo #10SPOILER
After travelling back into the past, you'll be in Chloe's kitchen at age 13. After having a conversation, grab the camera off the counter next to Chloe and her dad to take a picture of them.
Collecting all 10 photos will also reward you with the following achievement: