Cassie's rescue

Requirements

 * Don's errand quest is done
 * Fawn's secret life quest is done

Finding friends
You can't deal with Don on your own; firstly, you need some friends.

Preparing a plan
After learning about Fawn's hobbies, you can tell her about Cassie and the Don (the talk is only available when visiting her in the Condo, not in The Torture Rack), after which she would reveal that the Don is actually one of her club's patrons.

After resting, visit Fawn again and discuss with her the possible ways to deal with the Don. After talking about each possible option, you would come up with a plan of actions. She would give you an actual list of important details, which can be checked from inventory.

Fawn can be further asked about the Don's men's schedule, which adds up 20% to any chances when doing skill checks once inside the Don's hideout.

Civil unrest
Without the police involvement, saving Cassie would be impossible. Visit the local Police Station and talk with the girl called Arlene.

Unfortunately, police has sort of... "agreement" with Don: as long as he keeps the Slums in check, the police wouldn't bother him. But it's in your power to end this alliance.

Visit the Slums again, and find the local homeless (to the south from the Don's hideout). One of them would step out and demand lots of money, calling himself the "leader of the crowd", but don't agree on this just yet: this guy is a scammer.

If you refuse him several times, he would leave, allowing you to continue; otherwise, he may be found in the Gentlemen's Club, but would only return the 500 you need to finish the quest: everything else was already wasted on strippers.

People who stays after you deal with the self-crowned "leader" would demand those 500 to organise everything. Unlike the first guy, they may be trusted. Rest and wait until they do everything, then talk with them again.

While you were sleeping, the homeless have sparked a rebellion, spoiling Don's relationship with police and thus allowing Arlene to intervene. Go back to the police station and talk to Arlene – she will now agree to take Cassie into police protection if you rescue her.

From now on, you are technically ready to bust in, but you can make much easier by learning about Don's men's schedules. first opportunity arises immediately, since Fawn herself knows some of them as clients of her club. But there are two other girls who may help, too – Lin Lin and Sammy.

My kung-fu is better than your kung-fu
Lin Lin would only help if she gets paid first (300 ), but she significantly increases the chance of dealing with guards outside, or successfully stealing the key. Either option may be combined with asking her about guards' schedule, increasing your chances to pass skill checks once inside by additional 20% (adds up to your basic chance).

Hot bath
To receive help from Sammy, you need to befriend her first. Keep paying her for bath services (5 ) until she offers you a "special" for 40. After you accept it, she becomes friendlier towards you, and even offers to spar together sometimes.

After talking with her again after receiving an invitation to spar together, she would offer her help with saving Cassie. She can't do much, but she would tell you more about guards schedule, allowing you to bypass some of them. This would add additional 20% to all skill-checks when in hideout; this is cumulative with the bonuses from two other girls.

Getting inside
There are several ways to infiltrate Don's hideout, but all of them involve hard skill-checks.

To get it inside, you may steal the keys and try to sneak through, or you may deal with guards violently.

Skill checks are:
 * Attack guards; unsuccessful attack results in a Bad End.
 * Without Lin Lin's help: 10+(2*Str)% chance.
 * With Lin Lin's help: 50+(5*Str)% chance.
 * Steal door key: 50+(5*Spe)% chance.
 * You may only attempt to steal the key once. If you fail it, your only other option remains to deal with the guards.
 * After stealing the key, you may temporarily retreat if you are not confident that you can deal it with the current stats, or want to make additional save.
 * Allows you to climb the wall, bypassing guards entirely.
 * Seduce guards: (Ero 7+) chance.
 * Steal keys: 40+(3*Nim)% chance.
 * Attack them: 20+(2*Str)% chance.
 * Climb the wall (Strength 7+). Only becomes available after you obtain the key.

Finding Cassie
Once you infiltrate Don's hideout, you can try to bust through, persuade guards to just leave, or sneak past. Failing to do either result in a Bad End.

Skill checks are:
 * Charge in:
 * Without any help: 10+(0.5*Str)% chance.
 * With the help of only one girl: 35+(0.5*Str)% chance.
 * With the help of two girls: 55+(0.5*Str)% chance.
 * With the help of all three girls: 75+(0.5*Str)% chance.
 * Sneak through:
 * Without any help: 20+(1*Nim)% chance.
 * With the help of only one girl: 40+(1*Nim)% chance.
 * With the help of two girls: 60+(1*Nim)% chance.
 * With the help of all three girls: 80+(1*Nim)% chance.
 * Negotiate:
 * Without any help: 0+(0.34*Spe)% chance.
 * With the help of only one girl: 20+(0.34*Spe)% chance.
 * With the help of two girls: 40+(0.34*Spe)% chance.
 * With the help of all three girls: 60+(0.34*Spe)% chance.

If you didn't recruit Arlene, your fate depends on whether you dealt with guards downstairs, or not, but either way, it ends your game prematurely.
 * If you sneaked past guards, they would ambush you from behind once you confront the Don (regardless of choice), resulting in Bad End, as you would be captured.
 * If you knocked up guards, you may choose whether to fight the Don or try to negotiate with him. Again, either option results in his men catching up with you and attacking – but this time, you would be ready, initiating the battle with Don's guards. Either outcome would result in Bad End, but which one you receive depends on whether you win or lose:
 * Losing the battle leads to you being captured, resulting in the same Bad End as if you failed any other skill check while inside or were ambushed.
 * Winning opens the other choice (both of them would lead to Lust Doll and Cassie being forced to run from New Ark to save their lives):
 * Killing the Don results in police going after you.
 * Sparing the Don results in police and Don going after you.

If you did recruit Arlene, the quest continues.

Going out
If you either charged in or negotiated with guards, the quest would end immediately, with you going out without further resistance. Otherwise, the guards would try to block your way out, forcing you to deal with them again.

Skill checks are:
 * Charge in:
 * Without any help: 25+(1*Str)% chance.
 * With the help of only one girl: 45+(1*Str)% chance.
 * With the help of two girls: 65+(1*Str)% chance.
 * With the help of all three girls: 85+(1*Str)% chance.
 * Sneak through:
 * Without any help: 0+(2*Nim)% chance.
 * With the help of only one girl: 20+(2*Nim)% chance.
 * With the help of two girls: 40+(2*Nim)% chance.
 * With the help of all three girls: 60+(2*Nim)% chance.
 * Negotiate:
 * Without any help: 0+(0.34*Spe)% chance.
 * With the help of only one girl: 20+(0.34*Spe)% chance.
 * With the help of two girls: 40+(0.34*Spe)% chance.
 * With the help of all three girls: 60+(0.34*Spe)% chance.

Failing any of the sill checks would result in your capture and a Bad End.

Passing any of the last set of skill checks (or dealing with guards preemptively) allows you to evacuate Cassie from here, while Arlene steps in and... "deals" with the Don. In her own way.