Please help me find this old sex story

Hello all!
I need your help recollecting/finding an old story that I read either here or some other sex stories site. I only recall bits and pieces of it, so perhaps you people can help me out :)

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Here is the brief synopsis from what I can remember.

It is an Indian story, written in English.

It is about a mother-son duo traveling in an overnight bus. The bus is one of those seater-cum-sleeper ones. The bus is crowded, but there is one sleeper left, and the mother spends the night in that sleeper with a stranger. He fucks her multiple times.
The son at first only suspects something fishy is going on, and so decides to sit in the opposite seat below. From there whenever there is a light coming from oncoming traffic, he can see outlines.
During the bathroom break at the dhaba, the son meets the stranger, and without telling him that she is his mother, asks the stranger to put on his mobile phone light next time he is fucking her so that he can see.


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This is the major premise of the story. If anyone can find it and share it here, I'd be very grateful.

Thanks in advance.