N2
~ところに・~ところへ
At the time, When, While, Timing
車で左折しているところに、急に自転車が飛び出してきた。
I was making a left turn in my car when a bicycle suddenly came out of nowhere.
Explanation
It means 'just when I was doing ..., something unexpected happened'. The first part is what you were doing or about to do; the second is an event that barges in, usually a disturbance: 「寝ていたところへ電話が鳴った」 (Just as I was sleeping, the phone rang). The second part often uses verbs like 「電話がかかる、客が来る、雨が降る」.
Mixed up with
Dictionary form + ところへ: the moment you are about to do something. 「出かけようとしたところへ客が来た」 (Just as I was about to leave, a guest came).
ている + ところへ: interrupted in the middle.
た + ところへ: just after finishing. 「お風呂から上がったところへ宅配便が届いた」 (Just as I got out of the bath, a parcel arrived).
「ところを」 is followed by being found, stopped or helped: 「見つかる、呼び止められる、助けてもらう」.