Firefighters responded just after midnight to Old Town Road in East Setauket to find the home engulfed in fire.
There were also reports of people trapped inside, prompting a frantic rescue effort.
WATCH: Firefighters battle heavy flames and high wind in East Setauket
The woman who died was identified as 31-year-old Lisa Ostrowski, and her 10-month old baby boy and his father made it out alive.
The father escaped through a second floor window onto a roof ledge and handed his son to a good Samaritan below before he attempted to go back inside to save his wife.
But Stephen Otner, 30, was stopped by a wall of flames. He could not make it back through the fire again, and then jumped to safety.
"Really roaring fire," neighbor Tashim Jamel said. "Something really serious...really tragic what happened."
Ostrowski was found dead inside.
"The only thing that I heard was some woman screaming, and I was still on the phone with the dispatcher," neighbor Karina Schwarz said. "And I was like, 'There is a woman screaming in this house. I don't know where it's coming from, but I know that it's there.'"
The fast moving flames were fueled by strong wind gusts, presenting a challenge for firefighters.
"The wind definitively helped, because that's what caught the tree on fire," Schwarz said. "The wind blew it right into the tree. A power line even broke and started sparking on the other side of the driveway."
A charred pile of rubble is all that remains of the home.
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"It just doesn't make any sense," neighbor Lorna Schwarz said. "I wonder, did they have smoke alarms? What did they have in place?"
The father and son were rushed to Stony Brook University Hospital.
Otner has serious injuries and the baby has "a slight injury." Both are expected to recover.
The cause of the fire is not yet known. The investigation is ongoing, but so far, no foul play is suspected.
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