Well, Taken 2 is based on the concept of the family members of the killed villains wanting their revenge, and they are also ruthless in terms of this revenge. So, when Marko was killed, strapped to an electric cable and died of electrocution, his father wants revenge and promises that he will get the killer back to Albania, to suffer as the family of Marko has suffered. However, it is not clear as to who the killer is (after all, Neeson had killed almost everybody in the first movie), so Marko's father, Murad, goes to Paris, looking for the former intelligence friend of Neeson whose card was found near where most of the people were killed. He gets some information from this guy and then kills him and his family, and is now on the hunt for Neeson and his family.
Neeson is in Istanbul for a piece of work, and finds Lenore (ex-wife) and Kim (daughter) ready to surprise him over there. And then the action hots up. Kim wants Lenore and Neeson to go out for lunch while she would remain the hotel. However, Neeson spots them being tailed, and this starts the explosive action. He has to give up when Lenore is captured, but is able to warn Kim off, who just manages to escape the people hunting for her at the hotel. Later, when he has been captured, he is able to use a hidden phone (they did not search him for a hidden phone) to tell Kim to go to the American Embassy, but she refuses and persuades him to let her help, and he agrees (another weird thing, agreeing to put his daughter in danger). In the meantime, to make him suffer, Murad cuts Lenore's neck slightly, enough for her to bleed and hangs her upside down so that she can bleed in front of him.
The next part is fun - he tells his daughter that she has to explode grenades at regular intervals through which he will be able to use the sound to determine the location where she has to go to (seems a bit out of the world for me, but am not an ex-CIA operative, so maybe I do not know enough). She finally arrives at the house where he is, and he is able to get out and take Kim with him, but Lenore is recaptured.
Finally putting Kim in the safety of the US embassy, he is able to retrace the path and find where Lenore is, and after dispatching every other bad guy, he is finally left with Murad in front of his gun. He offers to let Murad go to end this killing urge, but when Murad agrees and then tries to kill him, he kills Murad (but thankfully, this does not form the basis for Taken 3).
The movie made a lot of money and the performances were also appreciated, but the surprised of the first film always makes it more difficult for the second film. Even though stuff such as using grenades to get location was a twist, the movie still seems to follow a regular script. You will like it if you like action, but it is not the same as the first version.