Need, dare and simple present

Hello,
I have read in an English grammar that the verbe to need and to dare follows the rule of the modal verbe to can and to must and don't taka an "s" at the third person.
We should write "he need" and not "he needs".

How ever, I have found in the novel 'The razor's edge'from Somerset Maughan the following sentence:
'...which persuades them that with this all that "needs" to be said is said'.

Is there a mistake in the novel or are the two spellings authorized?
There maybe have been a change in the rule.
What is the right way: he need or he needs?

Thank you.
Have a good day.
Serge