The gate was supposed to remain locked.
Nobody could accidentally wander into the pool area from the street.
He checked the latch.
It appeared secure.
Then he walked toward the side entrance.
The hinges were intact.
No obvious damage.
For a moment, he wondered whether he had forgotten to lock it.
He was certain he had.
But after a week filled with work deadlines and school activities, he could not completely rule out a mistake.
He checked the gate twice.
Then left for work.
The following weekend, another object appeared.
A silver bottle cap beneath the patio table.
It belonged to an expensive sparkling beverage he did not keep at home.
Then came a faint smell of perfume inside the poolside storage cabinet.
A displaced lounge chair.
A damp cushion.
And two wet footprints near the gate early on a morning when neither he nor his daughter had used the pool.
He began keeping notes.
Dates.
Times.
Weather.
Equipment readings.
Unfamiliar objects.
He did not accuse anyone.
He simply documented what he found.
Then the water bill arrived.
His household had used noticeably more water than the previous month.
The increase was not catastrophic.
But the engineer understood pool systems too well to ignore unexplained consumption.
Water loss could come from evaporation, a leaking fitting, a failing automatic fill valve, or an equipment problem.
It could also result from repeated splashing, cleaning, and topping up after heavy use.
He checked the system.
Inspected the accessible plumbing.
Reviewed the autofill settings.
Then arranged a professional diagnostic visit.
Nothing obvious explained the entire increase.
He began wondering whether somebody was entering the pool while the family was away.
It sounded ridiculous.
A private backyard.
A locked gate.
A quiet neighborhood.
But the objects kept appearing.
And when the homeowner mentioned the issue during an HOA meeting, the president responded in a way that made him suspicious.