Context : The elliptical galaxy NGC 3923 is known to be surrounded by a number of stellar shells , probable remnants of an accreted galaxy .
Despite its uniqueness , the deepest images of its outskirts come from the 1980s .
On the basis of the modified Newtonian dynamics ( MOND ) , it has recently been predicted that a new shell lies in this region .

Aims : We obtain the deepest image ever of the galaxy , map the tidal features in it , and search for the predicted shell .

Methods : The image of the galaxy was taken by the MegaCam camera at the Canada-France-Hawaii Telescope in the g ^ { \prime } band .
It reached the surface-brightness limit of 29 mag arcsec ^ { -2 } .
In addition , we reanalyzed an archival HST image of the galaxy .

Results : We detected up to 42 shells in NGC 3923 .
This is by far the highest number among all shell galaxies .
We present the description of the shells and other tidal features in the galaxy .
A probable progenitor of some of these features was discovered .
The shell system likely originates from two or more progenitors .
The predicted shell was not detected , but the new image revealed that the prediction was based on incorrect assumptions and poor data .

Conclusions :