This need is a modal verb: it always requires an infinitive without to; it doesn't have do-support in questions and negative sentences; and the third person singular (he/she/it) doesn't have -s. This is the need in your example.
It is slightly old fashioned. Except in negative sentences and questions, I don't think you will see it much in modern writing, except in certain fixed expressions, such as if need be ("if necessary").