Assassin's Creed II/Sequence 7: The Merchant of Venice

After the "Building blocks" memory, the next three open up at the same time and can be completed in any order. After "Monkey see, monkey do",

Benvenuto
A pretty simple memory, just follow Alvise da Vilandino around as he gives you and Leonardo a tour of this district of Venice.
 * Memory start: Talk to Leonardo right where the sequence starts.
 * Reward: 1,500ƒ, Assassination contracts unlocked

That's gonna leave a mark
As you're contemplating how to get into the palazzo, some thieves distract the guards and a woman attempts to scale the wall. She gets an arrow in her leg for her trouble and needs your help to get her to safety. Start out by following Rosa. She likes to fight anyone she sees, which means you'll also have to fight them while making sure she doesn't lose too much health. Eventually you'll run into a group of her thief buddies and you'll have to carry her the rest of the way. Don't bother stopping to fight, just keep going and let the thieves keep any enemies occupied. The only time you have to fight is if a pursuit guard follows you and at the end where you must become anonymous before dropping Rosa off.
 * Memory start: Enter the white marker to the west of the Palazzo della Seta.
 * Reward: 4,000ƒ

You'll hand her off to her friends, who will take her by boat back to their hideout. You need to go along with them and take out archers along the way who might damage them. Head down the left side of the canal they're going down and take out the soldiers along the way. When you run out of ground, free run along the beams on the sides of buildings to continue following the boat. Watch the minimap for red dots signifying a guard you should take out. This requires going back and forth between the two sides of the canal. It's best to stay a little bit ahead of the boat so they don't take any damage. When they make it out to open sea, get up above them and take out the archer on the corner of a far building. The next archers are down by the fast travel station, so drop down to take them out, then keep heading around the backs of the buildings facing the water. Shortly thereafter, you'll see them turn into an outlet and go under a building. Head over that building's roof and drop down to the small inlet on the other side to meet back up with them.

Go pick Rosa up and walk in the direction the camera shows you, then put her down on a table where indicated. Follow the quick time events during the cut scene after which you'll meet Antonio.

Building blocks
Nothing to it, just knock on the door to hae a conversation with Antonio and drink some coffee if you want.
 * Memory start: Knock on the door near where the last memory ended.
 * Reward: 1,500ƒ

Monkey see, monkey do
After watching Franco perform the climb leap, run up to the wall below the scaffolding and go up the same way. Perform three climb leaps to the top of the structure and enter the white marker there.
 * Memory start: Talk to Rosa in front of the thieves guild in the San Polo district.
 * Reward: 2,000ƒ, Climb Leap skill

Cleaning house
You'll need to take out three targets around the city. One is nearby to the northeast, one is down in the south east and one if very far to the east. You'll find the one nearby on a ship out on the water, accessible by a series of poles leading to it from behind the fast travel station. There are guards in two smaller boats on each side and a lot on the main one, so your best bet is to swim up to the main ship from underwater. From the fast travel station, wait until the closest guard and the target on the main ship aren't looking your way, then jump to the first pole and do a jumping dive underwater and swim to the side of the ship. You can turn your jump into a dive by pressing the legs button in mid-air. This should get you to the ship without being seen, after which you can climb the side and position yourself below the open section of railing where the target walks by. Do a ledge assassination when he comes around, then swim underwater back to the docks and head to the next target.
 * Memory start: Knock on the door to the thieves guild.
 * Reward: 2,000ƒ

The southern target is on the rooftops in the center of the green circle, and he will attack when he sees you. Head up there and take him out by stealth, push him off the ledge or just fight him normally. You'll find the final target in a market on the east side of the city. He's walking around with a friend of his and there are some groups of civilians you can blend with. Although there are plenty of ways to take him out, as he walks fairly close to both groups of people and a haycart, it's a good idea to get him when he stops at the edge of the canal so you can double-assassinate him and his friend at the same time.

Breakout
Three separate groups of thieves are being held captive somewhere in the city, each in a restricted area. One is directly south of where the memory begins, one is to the southwest and the last is in the northwest. The captives in the south are being guarded by a single soldier, but there are four guards stationed at the west side of the courtyard who will come to his aid if he's alerted. Climb down from the roof above him and assassinate him from the top of the cage they're holding the prisoners in. When you free the thieves, they will join you, and you'll need to take them back to Ugo. It's easiest to just go back along the streets so they don't get lost.
 * Memory start: Talk to the thief Ugo on the roof across from the east side of the Santa Maria Gloriosa Dei Frari.
 * Reward:

The captives in the southwest have two guards in front of the cage this time, and more guards at the entrances to the courtyard. Get up on the roof above the cage and perform a double air assassination from there. If this alerts anyone, just climb back up to the roof and throw anyone that comes up over into the canal. Alternatively, you could just fight all the guards. Either way, free the captives and either run through the streets or climb back up if you didn't clear out all the guards, then make your way back to Ugo.

The last area in the northwest has a single brute guard on the captives, but you won't be able to air assassinate him without being noticed. You can either go for it anyway and climb back up to the roof to let the alarm die down, or you can hide in the haycart and wait for him to come and poke around in there and do a stealth assassination. Either way, unlock the prisoners and take them back to Ugo to complete the memory.