The killer of EastEnders' Lucy Beale will be revealed in a live show on BBC One and RTÉ One which will be part of a special week of programmes to mark the soap's 30th anniversary next February.
The week-long anniversary celebrations will begin on Monday February 16, 2015 and will include one 30-minute live episode and "live elements" in the other shows.
BBC One Controller Charlotte Moore said: "Next February will mark a massive event on the channel by creating the ultimate 'doof doof' [theme tune] and finally reveal who killed Lucy Beale."
BBC Controller of Drama Commissioning, Ben Stephenson, said: "After a captivating year of drama in 2014, EastEnders will top this in February 2015 with the most ambitious anniversary any soap has attempted."
He added: "Live Week allows us to keep loads of secrets from the cast, crew and the audience until the very last minute. With shocking reveals and unguessable twists it's going to be a week that will change Albert Square forever."