  We present new spectroscopic observations in a field containing the highest
redshift cluster of the ESO Distant Cluster Survey (EDisCS). We measure galaxy
redshifts and determine the velocity dispersions of the galaxy structures
located in this field. Together with the main cluster Cl1103.7$-$1245
(z=0.9580; sigma_{clus} = 522 +/- 111 km/s) we find a secondary structure at
z=0.9830, Cl1103.7-1245c. We then characterize the galaxy properties in both
systems, and find that they contain very different galaxy populations. The
cluster Cl1103.7-1245 hosts a mixture of passive elliptical galaxies and
star-forming spirals and irregulars. In the secondary structure Cl1103.7-1245c
all galaxies are lower-mass star-forming irregulars and peculiars. In addition,
we compare the galaxy populations in the Cl1103.7-1245 z=0.9580 cluster with
those in lower redshift EDisCS clusters with similar velocity dispersions. We
find that the properties of the galaxies in Cl1103.7-1245 follow the
evolutionary trends found at lower redshifts: the number of cluster members
increases with time in line with the expected growth in cluster mass, and the
fraction of passive early-type galaxies increases with time while star-forming
late types become less dominant. Finally, we find that the mean stellar masses
are similar in all clusters, suggesting that massive cluster galaxies were
already present at z~1.
