"Alternative Methods" is a mission in Sequence 10 with Connor and Haytham Kenway when they stop working together.
It is important to have either the Double-barreled Pistol or a full stock of cartridges and Smoke Bombs for this mission if you are after full synch.
Do not touch the ground
Stop the Patriot messenger within 3 minutes
Stop the Kanien'keha:ka with non-lethal methods
Reach the old growth forest
Locate and neutralize the Patriot messengers
Reach the Kenien'keha:ka village and alert the Clan Mother
Prevent the Kanien'keha:ka from attacking
The Battle of Monmouth