"Ypres' wake-up call"
Ring the bell 3 times in Ypres.
You will have a chance to do this when playing as Anna in Ypres for the second time, when the town is attacked and the streets are filled with gas.
You will come across a church where you will climb up via ladders and unstable bridges. You replace the cogs underneath the bell to progress.
You must ring the bell to get one of the large cogs, if you ring it 3 times you will get the achievement.
This achievement is miss-able: the cog requires 2 rings, the achievement requires 3 rings.
(confirmation below: MysticWeirdo)