**Spoiler:**

His wife is obviously also home twenty minutes early.

This means she saved 10 minutes drive both ways to/from the station.

So she met him when she had still 10 minutes to go to the station, i.e. at 5:50pm.

He was walking from 5 till 5:50, so 50 minutes.

This means she saved 10 minutes drive both ways to/from the station.

So she met him when she had still 10 minutes to go to the station, i.e. at 5:50pm.

He was walking from 5 till 5:50, so 50 minutes.