British police say they may have stopped an al Qaida terrorist plot last week when they charged four Algerians with producing the poison ricin in their London apartment. Six other Algerians have also been detained. The men live in a section of London known as Little Algiers, which British police say has been infiltrated by radical Islamic activists and may be a site of terrorist sleeper cells. Documents were found in the apartment that appear to be copies of al Qaida weapons manuals found in Afghanistan. Ricin, made from castor beans, is fatal whether injected, inhaled, eaten, or even touched. There is no antidote.