Complex sentence: They all agree with the plan, and after working until 9:00 in the late evening, they are shocked to find the parking lot gates locked, directly resulted from Jim forgetting to tell the security guard that they were staying overtime.
Split into simpler sentences: They all agree to the plan, and after working until 9:00pm, they are shocked to find the parking lot gates locked. Jim had forgotten to tell the security guard that they were staying overtime.