Dead Rising Guide - Walkthrough
Part 1: Another Source
This is just a short cutscene. Be at the Security Room shortly after 4:00PM to view it. The monitor shows Isabela, the woman Frank encountered in the market, on a motorcycle. You have quite a bit of time to kill before the end of the next part of the case, but it might be a good idea to go ahead and complete it right now. If you leave the case for too long, even if it seems that you have an adequate amount of time left to complete, you may not.
Part 2: Girl Hunting
Avoid leaving this case for too long. Do not let the bar turn dark red. You need enough time to reach the area with the psychopath, and enough time to defeat her too. Time keeps ticking even during the fight. Thus, it would be a good idea to clear this mission immediately to avoid being stuck without enough time.
When you're ready to get started, travel to the North Plaza. The quickest way to the North Plaza and to this mission is through Leisure Park. Have "Girl Hunting" set as the active mission and follow the arrow to the location of the battle.
The biggest threat when facing Isabela is being struck by her motorcycle. One hit from the bike will reduce your health a fair bit, so try your best to dodge as she speeds toward you. Luckily, this is a very easy battle if you can find an area where she can't reach you on her motorcycle, and is therefore forced to use her Handgun to deal damage.
All you really need is a strong gun to defeat Isabela. The Huntin' Shack happens to be in the North Plaza, so you can make your way over there, grab a couple of Shotguns, and return to the fight. The difficulty here is trying to make it to the gun shop without being struck by Isabela on her motorcycle. When you gain control over Frank, start down toward the Huntin' Shack and keep an eye on your right for some scaffolding. Head up the ramp when you reach the scaffolding. Remain vigilant, however, as Isabela can make it up here with her motorcycle as well. She'll either head up the ramp after you, or speed to the opposite end of the scaffolding, ride up the ramp there, and then attempt to meet you head on. If this is the case and you spot her up ahead, drop down the side of the platform and continue toward the Huntin' Shack.
Duck into one of the rooms along the hall leading to the Huntin' Shack and blast Isabela from atop a stack boxes to quickly finish the fight.
Once you've made it to the gun shop, hop over the counter and grab a couple of Shotguns. Then, exit the store and duck into the first room to your left. Isabela should soon follow. There is a stack of boxes in the corner of this room. You can avoid Isabela's motorcycle by jumping up onto these boxes. Since this is such a small space, it is easy to hit Isabela as she drives by the boxes and crashes into the wall. Aim for her head to deal more damage. Use this method and Isabela can be defeated rather easily.
After the battle, Isabela agrees to get Frank an interview with Carlito. You'll need to return to the North Plaza at 12:00AM on the September 21st.
Achievement Tip: Stunt Rider -- If you have time to spare, this is your chance to unlock this achievement. Isabela leaves her motorcycle behind after her defeat. Hop on the bike, speed down the hall, and hit one of the wooden ramps. Doing so should unlock this achievement, provided the bike flies far enough (33 ft.).