  The second most significant detection of the Planck Sunyaev Zel'dovich
survey, PLCK~G287.0+32.9 ($z=0.385$) boasts two similarly bright radio relics
and a radio halo. One radio relic is located $\sim 400$ kpc northwest of the
X-ray peak and the other $\sim 2.8$ Mpc to the southeast. This large difference
suggests that a complex merging scenario is required. A key missing puzzle for
the merging scenario reconstruction is the underlying dark matter distribution
in high resolution. We present a joint Subaru Telescope and {\it Hubble Space
Telescope} weak-lensing analysis of the cluster. Our analysis shows that the
mass distribution features four significant substructures. Of the
substructures, a primary cluster of mass
$M_{200\text{c}}=1.59^{+0.25}_{-0.22}\times 10^{15} \ h^{-1}_{70} \
\text{M}_{\odot}$ dominates the weak-lensing signal. This cluster is likely to
be undergoing a merger with one (or more) subcluster whose mass is
approximately a factor of 10 lower. One candidate is the subcluster of mass
$M_{200\text{c}}=1.16^{+0.15}_{-0.13}\times 10^{14} \ h^{-1}_{70} \
\text{M}_{\odot}$ located $\sim 400$ kpc to the southeast. The location of this
subcluster suggests that its interaction with the primary cluster could be the
source of the NW radio relic. Another subcluster is detected $\sim 2$ Mpc to
the SE of the X-ray peak with mass $M_{200\text{c}}=1.68^{+0.22}_{-0.20}\times
10^{14} \ h^{-1}_{70} \ \text{M}_{\odot}$. This SE subcluster is in the
vicinity of the SE radio relic and may have created the SE radio relic during a
past merger with the primary cluster. The fourth subcluster,
$M_{200\text{c}}=1.87^{+0.24}_{-0.22}\times 10^{14} \ h^{-1}_{70} \
\text{M}_{\odot}$, is northwest of the X-ray peak and beyond the NW radio
relic.
