The Mystery of Dr. Elvarion's Protégé.

Following Popansa
If the party want to catch up to Popansa, they will need to perform an investigation check in the alleyway Popansa went down. Grewarum and Garrakas have advantage on this check as they saw him touch some bricks in the wall in a particular order. A successful DC 18 investigation check will reveal that some of the bricks have small glyphs etched into them. A DC 16 arcana check reveals that pressing the glyphs in a particular order will cause some sort of opening spell to activate. The party will notice that the center glyph is the least worn, the top and bottom ones are the most worn, and the side glyphs are moderately worn. The combination is up, down, up, down, right, left, center, right, left.
If the party are successful, a previously obscured manhole appears and swings open, the cover swinging up like a tin can lid. A ladder leads downward and into what looks like an abandoned sewer with no water in it. One end is bricked up and the other has a solid iron door. If the party knock at the door, a voice at the other end will ask for a password. The password is "Pleasure guides the powerful." The hideout belongs to the Chainmen and is a place for powerful people to satisfy their "base urges" on slaves as well as kidnapping people to be slaves. Mentioning Popansa will cause the guard to have surface thoughts of he being a benefactor. With a DC 15 persuasion check, the guard will believe that they are associated with Popansa.
In getting into the room, the party will be greeted by a cheery woman who asks them what their pleasure is. Four guards stand in the room with pikes and swords. There are two doors visible in the small antechamber and the ceiling is about 10 feet above the floor. Asking about Popansa, the woman will snap her fingers and a hidden humanoid will come forward and the woman will instruct them to go tell Popansa that he has guests. The humanoid will return and whisper to the woman, who will ask the party to accompany her. Going down a corridor, the party will enter a small room lavishly furnished. Popansa will be there alone with two guards with pikes who will not let the party come closer than 10 feet.
Popansa will say, "Well, well, well, you are persistent. You have found me. What do you want?" Popansa will scoff at the idea that he is Elvarion's bastard. He will say he is very close to Elvarion and that the doctor values his services sometimes. Popansa assures the party that he is not a bad person at his core. If the party try to attack him, the guards will attack and Popansa will cast a pass without trace spell and duck through a hidden tunnel. If the party does not try to attack him, they will be escorted out. If they try to press the glyphs again, the password will not work.
Talking to Dr. Harryfoot

On a low townhouse across the square from the temple of Garl Glittergold in the Golden Hills district is a brass plaque with the words "Dr. Galfast Harryfoot, Doctor of Exotic Biological Alchemy." Upon knocking at the door, a halfling woman dressed as a hospital nurse comes to the door and asks the party what they want. If the party mention Tindaleron, then a voice from within will shout, "Eh, EH!? Tindaleron you say? Send them in Hettie, send them in."
Dr. Harryfoot will ask the party, "Well, Tindaleron has something for me does he? What is it?" If the party ask about Mr. Popansa, Harryfoot will tell them that Elvarion is a fool to keep Popansa around. It is the reason he and Elvarion are no longer on speaking terms.
If the party ask Harryfoot about the trip to Toril, he will say that it was a good trip. He found some very rare plants. But he does not want to talk about what Elvarion did. All he will say is that Elvarion did something reprehensible and he will never forgive him for the "dark deeds" he committed in the name of science. Harryfoot tells them to ask Elvarion if they want to know so bad, but he is certain the old elf won't talk. He is taken with fits of coughing as he contracted an illness on the trip that he has come to terms with.
When the party report back to Tindaleron, he will tell them that he cannot get ahold of Dr. Elvarion because the doctor has left Dragonrock on a trip, according to his servants. Tindaleron ask them to remain vigilant for Mr. Popansa while he makes inquiries with Fairwind and Harryfoot now that they have made introductions for him. After a week, Tindaleron will send Yanny to fetch the party as he has news. He received an invitation from Elvarion to dinner and will meet them that evening after he meets with the doctor.
Tindaleron's Murder If the party does not go right away or they speak with these NPCs, they come to Tindaleron's house to meet the maid and some city guards investigating Tindaleron's murder. The maid says she saw Tindaleron coming down the street and a half-elf coming up the street. The half-elf attacked Tindaleron with a cane until he beat him to death. The maid then says she fainted. The city guard suspect Yanny, Tindaleron's half-elf clerk. Yanny has a letter from Elvarion that he was bringing to Tindaleron stating that he was sending Popansa away and he would be no trouble anymore.
Clues the party should have so far:

1. Popansa is half high elf. Yanny is half wood elf and has brown hair.
2. The maid recalls that the assailants hat flew off as he ran and that the street lights glinted on his hair, implying it is blond, not dark brown.
3. A broken off piece of cane is found scene that has a brass plate affixed to it with the inscription: To FE for Contributions to the DSoAS.
4. A hastly inscribed note 

Lieutenant Sokolov will be there arguing with the IEN's Provost Marshal about who has jurisdiction. The Streltsy argue it it a major crime and fall under their jurisdiction while the Provost claims it was elf on elf violence and is an internal matter to the base. Lieutenant Sokolov will tell the party that this is why he asked them to deal with the matter of the check and tells them that he will be indebted to them if they can investigate for them. The Provost will agree if Faddius is the lead investigator
If the party can get Yanny off, he will tell them that Tindaleron had gone to see Dr. Elvarion over Popansa's origins. He also reveals that Dr. Elvarion had wanted to extend a dinner invitation to the party as he had heard they were interested in Popansa. If the party do not get him off and try to go to Elvarion, Yanny will press some papers in their hands before they leave. It will be the dinner invite.
At Elvarion's house, he is noticeably agitated but says it is just nerves over hearing that Tindaleron was murdered. The manager was a good friend and he will miss him greatly. He says he is sent Popansa away because he is afraid that the reckless youth might seek revenge for the murder and is sailing on the Ocean's Queen this evening. He has a signed note from Popansa saying that he is leaving and won't come back.
A messenger will come from Dr. Harryfoot telling them that the doctor has died from his illness and that they should come to his home to retrieve a packet that they need to recover personally. At Harryfoot's house, there are several guards. Inside, the maid Hettie will have them come in, being the old, single doctor's heiress. She will unlock a drawer in the study after several precautions. She will tell the party that the contents of the packet she shall give them cannot be opened unless some unknown condition is met. Attempting prior will cause the contents to erase themselves. Harryfoot, however, wanted the party to have it. The packet consists of a note and a journal bound with arcane seals that show that they will destroy the contents of the book if tampered with.
Confronting Elvarion about the handwriting will result in the party meeting only his servants who say that he is not home and that he told them he went to the docks to see Popansa off.
If the party check with the docks, they will find that the ship sailed early in the morning and there was no way anyone could board it in the afternoon. If the party compare the handwriting from the note and the dinner invite, they will reveal that it is the same handwriting. He dots his elven script with small flourishes that are impossible to replicate.
After gathering all this evidence, the party will be drawn to Elvarion . If they come to his house, the servants will say he is locked in his study and won't come out. They are all very freaked out because they saw him go in but the voice now behind the door is someone else and they know that no one else could get into the room. If the party try and knock on his study door, a voice that is not Elvarion responds and tells them to go away. It sounds like Popansa's voice. Questioning the servants reveal that the office has been locked for hours after Elvarion went in there and no one could have come out without them seeing.
The door has an arcane lock but can be dispelled and the door broken down. If the door is broken down, a shot is heard as the door opens. Behind the door is a windowless room but a small hatch out into the street like a garbage shoot can be found. Lying on the floor is Elvarion in Popansa's clothes, dead from a gunshot wound. A loud click and a sigh like someone about to unburden themselves is heard and Harryfoot's journal unlocks.

Plot points/Scenes

Dr. Harryfoot relates how he and Elvarion journeyed to Chult on Toril to find a rare component in alchemy. Their hope was to find a steady supply that could be cultivated and they were successful, leading to their wealth. Elvarion, however, found something in a cave they explored. It was a fragment of an ancient text that talked about restoring humanoid forms. Harryfoot warned Elvarion that messing with the domains of divine beings seemed hubristic and wrong. Elvarion saw potential in restoring limbs without the need of clerics. 
Years later, messenger came to Harryfoot instructing him to bring the contents of draw to his house where a half elf will come to retrieve it. After that, Elvarion says he will explain if Harryfoot wants to know. The half-elf arrives and takes the chemicals, mixing a potion and asking Harryfoot if he wants this knowledge, but makes him swear to an unbreakable oath to secrecy. Harryfoot agrees and he see Popansa turn into Elvarion. Elvarion explains to a shocked Harryfoot that the recipe they found in Chult restores the form, but he could not get the right ingredients to turn him back into a full high elf. Harryfoot is enraged, telling Elvarion that he is working with dark sciences that no one should mess with and that Elvarion is dead to him. He wrote this down which partially violated his oath as he divulged the secret to a thing i.e. the pages he wrote on. Harryfoot is fine with that and hopes he can entrust the secret to someone so they can find that page.

Parent Plot

Coming to Dragon Rock