<step zero>
Before you can move forward with this plotline, you're going to need to build up Twig's trust. That means taking time to do nurse assistant shifts after work. You should take this time to participate in Dr. Twig's aphrodisiac trial and lower the potency to its minimum. You can work on these simultaneously. There is an alternative to bypass the aphrodisiac trial if you own the gas mask purchasable in the General Goods store at the Mall.
<step one>
After you have rescued Dr. Synthea, have a therapy session with her. She will approach you about taking down Dr. Twig.
For more information about rescuing Dr. Synthea, click here.
<step two>
Tell Dr. Synthea that you are ready to take down Dr. Twig. If you are not ready, you can talk to Synthea about taking down Dr. Twig after your weekly appointment on Friday. Once you've agreed, go about your business as usual.
<step three>
While on your way home from work after agreeing to take down Dr. Twig, you will be summoned to his laboratory while trying to leave work in the elevator. You will encounter Dr. Synthea and Candy bound to different tables as Dr. Twig prepares to inject them with a new serum.
<step four>
You will have two options, plus a third if you have a certain skill.
"Press the button to administer the drugs" - This will delay attempting to defeat Dr. Twig. You will encounter the elevator event again later.
"Hit the button marked "emergency patient release"." - This will push the event forward.
"Why complicate things? Just punch the asshole." - This option will appear if you have any of the following combinations of skill points. Taking this option will skip steps five and six.
Martial Arts > 10 AND Strength > 15
Martial Arts > 15
Strength > 20
<step five>
Dr. Twig will release the gas into the laboratory. If you have lowered the power of the aphrodisiac strength, Synthea and Candy will subdue Twig. If you have the gas mask in your inventory, you can subdue him yourself no matter what level the gas potency is. If the gas is too strong and you do not have the mask, you will trigger a bad end.
<step six>
After subduing Dr. Twig, you will have the option to turn the gas off or flood the building with it. Flooding the building with the gas will trigger a bad end (unsurprisingly).
<step seven>
With Twig at your mercy and the gas disabled, you will have three options for deciding Dr. Twig's fate. With him out of the way, the plotline is completed.