This was horrible.

Of course it might be another hippopotamus, or a crocodile, or a lion--or, in fact, almost anything.
'Keep your hand on the charm, Jane,' said Robert hastily.

'We ought to have a means of escape handy.

I'm dead certain this is the sort of place where simply anything might happen to us.' 'I believe a hippopotamus is going to happen to us,' said Jane--'a very, very big one.' They had all turned to face the danger.
'Don't be silly little duffers,' said the Psammead in its friendly, informal way; 'it's not a river-horse.

It's a human.' It was.