Augusto Pinochet won't be in London for much longer, so the lawyer leading the case against the dictator needs to act fast if he is to secure the help of the UK authorities. But the Spanish judge in charge of the investigation is moving too slowly.
Meanwhile, there are powerful figures in the Spanish legal establishment trying to block the case, and the former Chilean dictator himself - now aware of the moves being made against him - has been applying pressure to shut it down.
So the lawyer takes a professional risk and looks to a different judge for help - one with a reputation for fearlessness and ruffling feathers.
The Arrest is presented by Philippe Sands. The series producer is Simon Tulett. Sound design and mixing is by Tom Brignell. The production co-ordinators are Helena Warwick-Cross and Tammy Snow. The editor is Matt Willis.
Philippe Sands is the author of '38 Londres Street: On Impunity, Pinochet in England and a Nazi in Patagonia'.