'Fringe': 'Letters of Transit' in pictures
This dramatic instalment - featuring Henry Ian Cusick (Lost's Desmond) as a guest star - is shrouded in secrecy. But here's what we do know - the year is 2036 and the Observers are on the offensive! Who will survive the terrifying onslaught?
Fringe continues on Friday at 9/8c on Fox. In the UK, the series airs on Sky1.
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Photo gallery - view images from 'Letters of Transit' below: