did nothing to punish the rapist except slap him across the face.

[GoodTaste]

Even when Rabe caught a Japanese raping a woman in one of the backyard straw huts, a military officer did nothing to punish the rapist except slap him across the face.

Source: The Rape of Nanking by Iris Chang (p120)

Is the tense of the word "slap" correct here? It seems to me that it should have been "slapping" or "slapped". I am not absolutely sure.

 

[emsr2d2]

The original is correct. After "do/did nothing except/but ...", we use the bare infinitive.

I did nothing except eat yesterday.
They did nothing except sleep on their holiday.
We did nothing but dance at our wedding.
She'll do nothing but moan all day long - I guarantee it!