1987. Tan Keng Hock, 23, sleeps on a foldout

mattress in his late uncle’s 3room HDB flat in

Toa Payoh, surviving on kaya toast and the last

of his NS savings. He tutors maths to three kids

from Block 217—Chen Mei Ling, Lim Wei Jie, and

Fatimah binte Ali—each paying $15 a week in

crumpled notes. The flat smells of old rice and

mosquito coils. His only tool: a chalkboard

nailed to the wall, a ruler, and a thermos of

weak TehC.

The building’s rule: no more than one tuition

teacher per floor. Not written. Not posted. Just

known. Old Mrs. Tan from Block 215 vanished when

she hired a second tutor next door. Her students

all scored A+—then stopped speaking. No one

talks about it. Keng Hock doesn’t care. He’s too

hungry.

Then the chalk moves on its own.

He wakes to a perfect quadratic solution written

in his handwriting—except he didn’t write it.

Next day, Mei Ling solves a calculus problem she

never learned. Wei Jie recites the entire

Periodic Table in Malay. Fatimah dreams in Tamil

equations. Their parents throw parties. Keng

Hock’s bank account swells. He buys new shoes. A

real bed.

He finds the ghost in the void behind the toilet

panel—skeletal, in a faded 1970s school blazer,

fingers still stained with blue ink. The ghost

doesn’t speak. Just points to the chalkboard.

Keng Hock understands: the building remembers.

Only one teacher can live here. Two teachers?

The building eats the weaker one.

He tries to quit. Stops tutoring. The kids fail.

Their parents scream. One father throws a chair

through the wall. Keng Hock knows—he’s the only

one who can fix it. He invites the ghost to sit

beside him during lessons. The chalk writes

faster. The students’ scores hit 98%. The

neighbours start leaving offerings: oranges,

incense, a pair of spectacles.

On the night of the final exam, Keng Hock lights

three joss sticks. He gives the ghost his last

$50 note—bought from his own tuition fee—and

whispers, “You taught them. I just let you.”

The next morning, the ghost is gone. The

chalkboard is clean. The kids get their results:

all A1. Keng Hock opens his bank book. $12,000.

He buys a oneway ticket to Johor Bahru. The

building doesn’t stop him. The rule was never

about money. It was about space. One teacher.

One soul. One flat.

He leaves the thermos. The neighbours say the

new tutor who moved in last week? Her students

never score above 60. The ghost never came back.

Keng Hock opens a hawker stall selling kueh. His

son will be a doctor. He doesn’t teach anymore.

But every night, he hears chalk scratch against

wall. Not his. Not his.