This achievement is awarded after completing the following missions in Sequence 7 - Underworld with at least 50% synchronization:
Memory 1 - The Hidden City
Memory 2 - The Spy Who Shunned Me
Memory 3 - The Renegade
Memory 4 - Decommissioned
Memory 5 - Last of the Palaiologi
Memory 6 - Escape
Memory 7 - Passing the Torch
For those of you going for
there are some videos posted below that should help you achieve 100% synchronization in each memory. The videos do not belong to me and I do not take credit for them.