Click on the door in Lower Jeuno at G-11 (on the second floor) for a cut-scene.
Go to Qufim Island and follow a path down the cliff to F-8. Be warned that a Kraken spawns right on top of the flowers, so approach to a safe distance and wait till 22:00. After 22:00 (until the night ends) use sneak to approach safely and click on the Night Flowers for a cut-scene.
Note: The flower will spawn at 1700, but will not be ready to harvest until 2200 thru 0000 (Midnight) Vana'diel time. After Midnight the flower will have lost it's magic and wilted, meaning you have a very short window to access the Cutscene.
Note: If attempting this quest at lower levels, it is recommended to reach the path before 22:00 as Banshee's appear once night falls. Also note that the recently added Goblin Bounty Hunter runs down the path that leads to the Night Flowers and the Kraken so be extra careful.
After the cutscene, return to Lower Jeuno and click on Dietmund's door again (G-11).
His son will come out and give you your reward.
Next is Last step to get Beastmaster job..... check next quest :) .