From the kitchen window, it looked like someone in the unit directly facing her block had placed some clothes outside the window to dry.
But when domestic helper Nani Sulastri, 27, gave the same spot a second look, she gasped as the "clothes" started moving.
It turned out that a woman in her 30s was perched precariously on the parapet outside her fifth-storey flat at Bukit Purmei Road.
And this was not just some "ordinary" perch.
The woman was standing on a small blue stool - only slightly wider than a tissue paper box - which had been placed on the narrow parapet.
This incident happened on Tuesday at around 12.10pm, a Singapore Civil Defence Force (SCDF) spokesman said.
Speaking to The New Paper on Thursday, Ms Nani said she was horrified by what she saw.
"It's so dangerous and I was very scared for her. I didn't even dare to think what would happen to her if she had fallen down," Miss Nani recounted.
She added that she has read in the news about maids falling while cleaning windows, but this was the first time she had seen something similar.
As a domestic helper herself, Miss Nani, an Indonesian, is well aware of the dangers of cleaning windows.
"We must be very careful (when cleaning windows). My employer told me that I cannot clean the windows when there's nobody at home," she said.
Miss Nani, who was then airing the laundry, said she alternated between completing her task and watching the woman's every move.
She added that the woman, dressed in a black top and white shorts, had first stood outside on the ledge and tried to wipe the windows.
When she could not reach the higher parts of the window, someone from the flat passed her a stool.
Ms Nani then watched in horror as the woman placed the stool on the ledge and tried to climb on top of it.
"She tried to balance it on the ledge, but the stool started shaking. It was still too low for her (to reach the higher parts of the window)," she said.