It's not an easy thing having to come in to a project which is already heading in the wrong direction.
On the plus side, when you are asked to come in and deal with projects gone wrong it measn you are regarded as a cut above the rest and that management have faith that you are the person with the talent and skills to deal with it. You are moving into a new level of your career.
One of the first things that I would do would be to produce a realistic project plan based on the work still to be done, and be open and honest with your stakeholders. If the deadline is 2 weeks away and there's 3 months of work left you need to highlight this. I wouldn't bust a gut (and kill the project team) trying to meet the original timescales.
I agree with Craig - "you are regarded as a cut above the rest and that management have faith that you are the person with the talent and skills to deal with it"
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