gta4.net has a very descriptive walkthrough of the first 5 missions of Rockstars upcoming game, Grand Theft Auto IV.
"A ringtone can be heard when the call is made. Niko needs to get closer to figure out where it is coming from. The blackmailer must be identified and killed. Since this was carried out in broad daylight, a two-star wanted level is gained. Niko must evade the cops and return the memory stick to McReary in order to complete the mission."