THE FEAT: She predicts that an important figure will be in great danger of being crushed to death when he/she take part in a special ritual.

EXPLANATION:

First, she connects a fire incident, a mysterious will concerning 3 craftsmen, and the recent death of an official together.

The fire incident:

A fire had burned through a food storehouse with no witnesses or ideas to how it started. Finding a pipe on the ground and knowing the storehouse most likely had flour kept in it, she deduced that the fire started because someone smoked a pipe with flour in the air, causing the flour to ignite.

The 3 craftsmen:

A metal working craftsman recently died, leaving one of his 3 sons as his successor with one problem: none of them know his secret technique. Just before the craftsman dies, he leaves a will that goes like this: 

TO THE ELDEST SON GOES A DETACHED WORKSHOP, TO THE MIDDLE SON A CRAFTED PIECE OF FURNITURE, TO THE THIRD SON A FISHBOWL and 'YOU SHOULD ALL HAVE TEA LIKE YOU USED TO WHEN YOU WERE YOUNGER.'

When Maomao enters a room with the 3 brothers, she notices a number of things: 

1. The room has an unusual construction

2. There's a dresser in the middle of the room that is in the way

3. The positioning of the table and window (which is also longer than usual) is strange

4. The dresser has rounded off corners, and metal keyholes, which were made with different metals.

5. The window in its odd positioning, only allows some sunlight to enter; most of the sunlight is filtered by the tree leaves outside.

6. A mark on the shelf in front of the window shows that something has been placed there for a long time.

7. The three heirlooms are quite valuable but useless (the fishbowl made of glass, the 'piece of furniture' is a dresser fastened to the floor with a useless key for the keyholes, the workshop being useless with the dresser in the way)

After noticing all of these things, tea is prepared and Maomao notices again that the three brothers instinctively move towards specific seats, which all avoid being in front of the window. She immediately figures out that everything must have a purpose, so she tells the brother to put the fishbowl where it used to belong, fills the bowl with water and waits. The result is the sunlight, which is now concentrated into a single ray by the water, has a clear path to onto of the keyholes and shines into it. The sunlight is then blocked out by the tree's shadow. When the light is gone, she smells something strange, and deduces that the sun's beam must have heated something and melted it, so she asks the brother to open the keyholes with the key to find a mold of a different key (this key was made from the metal filling the keyholes which melted into the mold when heated). Using the new key, she opens the drawers to find a 3 different metals, which the youngest brother takes interest in. By seeing he has the worst burns among the brothers, which are associated with metal work, Maomao knows that the youngest brother understands the secret recipe, which uses the 3 metals in a certain ratio.

The deaths of the officials:

A case is presented to Maomao concerning the death of an official; the death of an official ten years before also had the exact same conditions: they both died with blowfish symptoms. The cooks, however, denied using blowfish and since the blowfish skin and organs were found in the bin, it was declared true that the officials couldn't have died of blowfish poisoning (as only the skin and organs are poisonous). After finding out that seaweed was used in the official's meal, she visits the offical's house and finds out that a jar of seaweed was there that had been used before getting kicked out from the house and taking a sample of the seaweed. She then explains that the seaweed was not from the local area based on its harvest time and time of preservation and was poisonous but could be made edible if soaked in limewater; it is then shown that the death was intentional, as the official did not purchase the seaweed himself, and was therefore fed it by somebody else wishing to kill him.

Now with these incidents explained, all that's left is how she deduced the plan to assassinate a person taking part in a ritual.

1. The officials who were targeted and killed were both involved in ritual implements, so their deaths would greatly profit anyone trying to meddle with the rituals.

2. The fire would have produced an excellent diversion to steal ritual implements.

3. Since the implement was actually a huge beam hanging from the surface, it would be easy to kill someone by dropping it on them if they were inside the tower. The beam is usually lowered up and down but has strong fittings and fasteners, making it look impossible to drop the beam.

4. Since the implements were stolen, they of course had to be remade.

5. The former metal worker died leaving the recipe for his youngest son (the recipe for an easily melting substance).

6. The ritual also involves a brazier, which means there will be a fire near the ground for the brazier.

7. The fire near the ground might melt the fasteners (which are made of the easily melted substance) on the ground, which will lead to the giant beam falling on top of the person in the ritual.

8. There is a ritual today, which means the person inside is in danger of being crushed.

This feat shows impressive reasoning, thinking, foresight and AC (as Maomao is a maid in the court, so she was unable to enter the tower to directly stop the ritual from happening and had to face constant problems throughout the entire thing).

An underrated character's feat