Final Fantasy 7 Remake Secret Medicine is a side quest available in Chapter 14 of the game. It's another fetch quest which requires you to find ingredients for a doctor crafting medicine. This one requires a previous quest, Subterranean Menace, to be completed as one of the bosses holds an ingredient.

You can pick up this quest from a doctor in Sector 5 who stands across from the community center. Fortunately, the first one is easy and provides momentum for you to grab the others. Your reward for this is a Teluric Scriptures Vol. III which provides some points for Aerith.

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Final Fantasy 7 Remake Secret Medicine Locations

The first item you'll want to grab is the Moogle Mortar, so the doctor can make the medicine in the first place. You can find this key item in Moogle Emporium shop in the Kids' Hideout. Make sure you've got enough money around to purchase it.

The second item is located in the Sector 5 Church where Cloud and Aerith first met. You'll find Medicinal Flowers growing near the building—your second key item in this quest.

The third item is a bit more complicated. You'll need to either have completed or are currently completing the Subterranean Menace quest in order to get this last ingredient: a Behemoth Horn. The Behemoth is the last boss in the aforementioned secondary quest.

The Behemoth Type 0 boss is a powerful and dangerous beast so it may be worth your while to double check your HP and healing items before taking it on. Players have reported the best success in this fight by keeping out of its range. Collect the horn from its corpse when you're done.

Returning these items to the doctor completes the quest and gets you your reward: Teluric Scriptures Vol. III.