What is the Story of this Movie?
It starts one month after Star Trek Nemesis at the Starfleet Academy where Doctor Crusher from Starfleet Medical is visiting the new Academy Admiral, Jean-Luc Picard. She tells him that through a new sensor prototype unusual information was found on B4's memories. The memories came from Doctor Soogn and were meant for Data. They also found out that
B4 is not a prototype as originally thought. Doctor Soong built B4 later than Data and only for the purpose of protecting Data, at any cost.
B4 received much information from Data and it seemed that he integrated Picard in his protection program too, or he knew what Data would do in that situation and that there was only one way to fulfill his mission to protect Data, sacrifice himself. It was not found out how or when B4 changed position with Data, but one thing is sure, B4 and not Data was destroyed with the Scimitar.
After the danger was over, B4 should have sent a signal to Data to reactivate his personality, but through the big explosion this signal never reached Data, so his personality is still deactivated and he is working with the B4 transferred personality. Only two devices are able to reactivate Data, one of them was destroyed with B4. The other one Data owned a long time ago, but it was forgotten on board of the Enterprise-D.
Admiral Janeway from Starfleet headquarters transfers the command of the Enterprise-E back to Admiral Picard for this special mission: To fly back to his old ship on Veridian 3 to find the device. Unfortunately the Veridian System is owned by the Breen since the Dominion war, and now a very dangerous area. Ambassador Spock heard about this mission through some special ways and wants to use this unique chance to bring the mortal remnants of Captain Kirk back to Earth. Because the Enterprise isn't completely repaired and only has a full crew with the addition of several cadets, three other ships escort them; one of them is the Titan of Captain Riker.
On the way to the Veridian system a distress call is received and the Titan has to find out where it is coming from. They discover some sort of temporal anomaly where Captain Sulus Excelsior is caught. Because of different reasons Commander Uhura and Commander Chekov are aboard the Excelsior also. After they heard that Kirk was found and Spock wants to bring his mortal remnants back to Earth, they decided to join this mission, but they have to leave the damaged Excelsior behind for now and fly with the Titan.
That's enough story preview ;)