A Gift of Nightshade
Requirements
Talk to Wabbin to begin the quest.
Walkthrough
For the first step, he wants a Blue Nightshade. Hand him one.
Then go talk to the woman on the other side (twice) to complete the quest. You'll get 120 rupees.
Tip: If you have done the Slated for Upgrades Side Quest and have Sensor+, and already have a picture of a Blue Nightshade, you can set it as your Sensor+ target for help in finding one.
Bonus Tip: If you don't already have a picture of a Blue Nightshade, and if you have done the Sunshroom Sensing Side Quest as well, you can talk to Symin at the Hateno Ancient Tech Lab and purchase materials pictures for your compendium (at 100 rupees each, getting a random picture each time, can buy in bulk if desired) until you have a picture of a Blue Nightshade. You can then set it as your Sensor+ target for help in finding one.