Assassin's Creed II/Sequence 10: Force Majeure

An unpleasant turn of events
You don't have to do anything for this memory, just watch the cut scene.
 * Memory start: Enter the white marker inside the Palazzo della Seta.
 * Reward: 2,000ƒ

Caged fighter
Head north to rescue Bartolomeo D'Alviano from his captors. The whole area surrounding him is a restricted area, so stick the rooftops and take out the archers up there are you approach. His cage is on the northern side of the restricted area, and if you approach directly from the south, you be able to come up behind two guards on the roof above for a double-assassination. If the archer on the north side of the building Bartolomeo is in sees you, just run back the way you came and drop down over the side of the roof until his alert status goes away. Afterwards, run up and assassinate the last archer while his back is turned. When the archers are taken care of, you'll need to take out the four guards on the ground in front of the door on the west side of the prison. Jump down for a double-assassination, then either throw a smoke bomb to finish off the other two, or just fight them normally. Alternatively, you can climb down the side behind them until they're alerted, then quickly climb back up and stay out of sight until the alert dies down. This will split the group up and you'll have the opportunity to get them either one on one, or in double-assassinations.
 * Memory start: Talk to the wounded man on a rooftop balcony in the Castello district.
 * Reward: 4,000ƒ

When you've taken care of the guards, open the gate and you'll be attacked by three more of them. When you've taken care of them, you'll need to head back to the south, almost exactly where you started the mission. On the way, Bartolomeo will try and fight anyone he sees, so quickly dispatch any enemies so he doesn't get hurt and he'll follow you again. When you get back to the objective shown on your map, you'll see a white marker you can enter. This time there are only two guards waiting, so take care of them and head into the Quartier Generale di Bartolomeo D'Alviano.

Leave no man behind
This is another rescue mission, where you'll need to free some of Bartolomeo's men who have been captured. Head to the east to find the first cage guarded by three soldiers. They shouldn't present much of an obstacle, so take them out and free the prisoners. The next location is to the northeast, and four of the soldiers you freed will accompany you. They'll end up fighting any guards they see, but it's up to you whether you want to help them out or just go unlock all the prisoners on your own. You'll have to be anonymous to open a cage, but it could be quicker if you don't have to wait for the other guys. Head to all the cages and kill the guards in front to complete the memory.
 * Memory start: Knock on the door to Bartolomeo's room at his headquarters.
 * Reward: 4,000ƒ

Assume the position
Take a group of Bartolomeo's men and clear out different areas of the city to set them up where they can cause some havoc. The first location is directly to the north of you and consists of two brutes and two lightly armored soldiers standing in a little alleyway. You can climb the wall on the side of the group to air assassinate both brutes, which will make the fight a little easier, but it should be enough to just run up and get one of them before stabbing the rest while they're engaged with your buddies. When they're all down, a white maker will appear that you'll need to step into.
 * Memory start: Knock on the door to Bartolomeo's room at his headquarters.
 * Reward: 4,000ƒ

The next location to the southeast has three guards tucked away behind some walls off the main street. Take them out and enter the white marker that will appear. The last location just has two guys who can easily be taken out with an air assassination from the roof above. Enter the final white marker to end the memory.

Two birds, one blade
Just across the canal to the east, is white marker located on top of the cross at the top of a tall building. Climb up and enter the marker and you'll see the signal go up, meaning that the attack is on. You'll see that he's fighting Dante and needs some help, so dive off the tower into the canal and head over to the fight. As soon as you get there, Dante takes off back to the Arsenale and you'll need to take out the two brutes Bartolomeo is fighting. When they've been dispatched, follow Bartolomeo as he chases after Dante. When you get over in front of the Arsenale, you'll be tasked with defeating Dante. You're not allowed to just assassinate him or poison him – in fact your pistol has no effect either. You'll have to either beat him with your blades or put five throwing knives into him.
 * Memory start: Knock on the door to Bartolomeo's room at his headquarters.
 * Reward: 8,000ƒ, Letter to Dante Moro

However you do it, when Dante has taken enough damage, Silvio Barbarigo will call Dante off so they can retreat back to their ship. When you regain control, you'll have 4:50 minutes to chase them through the Arsenale and take them out. You can do this in many places, as they stop to look around a lot and there is plenty of opportunity to get above them for air assassinations. As you chase after them guards will be blocking your way, so climb up whatever's nearby on the sides to get past them and catch up to your targets. You can complete this assassination in about fifteen seconds by simply following them, running up the first crates with sheets to the right of the first blockade, then air assassinating them from the platform above them when they stop.