Don's errand

Since you likely don't have any money on you yet, you can't just buy a pass into New Ark City. However, the guy standing nearby talks something about other way — through the sewers. Eww. After following through the sewers, Lust Doll reaches the New Ark Slums.

Don't screw with Don
The only exit from here is guarded by some bandit who demands 5 for every passage. To progress further, Lust Doll must somehow get past him without paying — either by having at least 5 Strength to push him, or at least 5 Speech to trick him.

The next time you would visit that checkpoint after taking some rest, Don's guys would find you and bring to their boss, who would demand not just the money you didn't pay, but also "a fee", resulting in 200 "fine" this time. Paying up would just reset him. Saying that you're broke would result in him whoring you out. The only way to progress is so offer to work out the debt. Attempt to resist the Don, and choosing to fight would result in your getting killed, and abrupt Bad End.

Don doesn't need assassins, while picking sex job only results in Lust Doll being put to use a gloryhole, and resets the encounter; to progress, a grunt job must be picked. Choosing to resist at the start, but backing up after Don admits that you have guts would result in you automatically picking the grunt job. "Grunt job" is simple – find one particular cat-girl, runaway sex slave, and bring back "Don's property".

Runaway pet
If you still didn't make it into Cassie's safehouse, do it now.

To progress further, warn Cassie about the Don going after her. Unfortunately, this amounts to nothing: Don decided to not trust you, and just sent his men to follow you and learn where Cassie hides; the moment you would go to sleep, Cassie would be abducted.

When you would re-visit the Don, he would offer you 500 as a "reward". You can accept or refuse, but it wouldn't affect subsequent plot in any way.