There are a total of
10 peepholes you will need to look in for this trophy:
1) The
front door - look in this one when you approach the house for the first time.
2)
Edie's door (the library) is next to the front door. You can look in it the first time you enter the house through the garage.
3)
Sven and Edie's door - on the first floor landing. You can also access this peephole the first time you enter the house, before starting any of the Finch's stories.
4)
Calvin and Sam's door - next to peephole 3)
5)
Gregory's door - next to peepholes 3) and 4)
6)
Barbara's door - also accessible on the first floor landing before starting any of the stories.
7)
Molly's door - also accessible on the first floor landing before starting any of the stories.
8)
Telescope by the sea - Accessible after playing through Walter's story and exiting the house. You find this at the end of the cliff after passing through the pet cemetery and going past the statues.
9)
Milton's door - After playing through Gus' story and making your way up to the top of the house you will cross a wooden bridge and see the door in front of you.
10)
Lewis' door - After playing through Milton's story, you will climb another set of steps and follow the walkway straight to Lewis' door.
Make sure you look in each peephole for a few seconds until Edith has finished speaking, or looking in the peephole will not count.
Maka91 has done an excellent video walkthrough for this trophy: