SQL- A query doesn't show me data

Question

I have a table people with fields "id" "name" and "p_father" I want to select records where the "id" field does not appear in the column "p_father"

I try this query

select * from people where (id  not in (select p_father from people));

But this doesn't show me any results. However if I use this query

select * from people where (id  in (select p_father from people));

It shows me all the records except the one I wanna select

Thanks!