  In a paper titled "Asking photons where they have been?" \cite{LV} Danan,
Farfurnik, Bar-Ad and Vaidman describe an experiment with pre and post selected
photons going through nested Mach-Zehnder interferometers. They find that some
of the mirrors leave no footprints on the signal and interpret this as evidence
that the photon skipped these mirrors. They argue that the experiment supports
Aharonov-Vaidman's formulation of quantum mechanics \cite{AharonovVaidman}
where post-selected particles are assigned disconnected trajectories. I review
the experiment and analyze it within the orthodox framework of quantum
mechanics. The standard view of interfering trajectories accounts for the
experimental findings.
