Double alarm for Christoph 9

A motorway accident with several seriously injured people sends the Christoph 9 crew taking off under high tension. Shortly before reaching the accident site, however, there’s a sudden change: dispatch orders them to return. No sooner have they landed back at the station than the next alarm comes in: another traffic accident, again in the same area. What will the crew find when they arrive? Also: a basement fire in a high-rise building. The fire brigade must evacuate all residents before the toxic smoke spreads through the stairwells.