Tonally similar to the French horror picture Them, this is nasty, gritty and efficient when it comes to delivering the thrills and chills.

As a tribute to master-scaremonger John Carpenter this is promising...

F is unlikely to prove a core-curriculum choice for cinema auds.

The film is scary, the tension well sustained, and it all ends deliberately up in the air, probably to suggest that this was an exercise in pure terror.