Anyone who watches Person of Interest will know that epsiode 17 of the present series was not shown by Channel 5. Although Channel 5 say they intend to show it later in the year, they haven't said when.
In the last day they have put it on their Demand 5 so that we can watch it now online rather than having to wait.
http://www.channel5.com/shows/...sodes/episode-17-258
Note that it's only available for 11 days.