Stranger Than Normal

Some people claim that extra-terrestrials are already here among us, but how would we recognise them if they don't look very different to ourselves? We are such a diverse people that, when anyone diverges from the norm - whatever that is - by what means would we identify them as stranger than normal?
Juv is an accidental guest of a government research installation, where his 'alienness' is for a time obscured by the nature of the clandestine undertakings being pursued there. When a threat to the entire planet is revealed, he resorts to a very human response to avert disaster.