  We present near-infrared (1-2.5 micron) JHK photo-spectroscopic results of
the unusually slow nova V5558 Sgr (2007). V5558 Sgr showed a slow climb to
maximum that lasted for about 60 days and then underwent at least five strong
secondary outbursts. We have analyzed the optical light curve to derive large
t2 and t3 values of 281 +/- 3 and 473 +/- 3 days respectively. An alternate
approach is adopted to derive a distance estimate of 1.55 +/- 0.25 kpc as
conventional MMRD relation may not be applicable for a slow nova. In the
pre-maxima stage the spectra showed narrow (FWHM ~ 400 - 550 km/s and strong
emission lines of Paschen and Brackett series with prominent P-Cygni
components. In the later phase the spectra show significant changes with the
development of strong and broad ~ 1000 km/s emission lines of HI, HeI, OI, and
NI and some uncommon Fe II emission lines. No evidence of dust formation is
seen. V5558 Sgr has been shown to be a rare hybrid nova showing a transition
from He/N to Fe II type from optical spectra. However the near-infrared data do
not show such a transition and we discuss this anomalous behavior. A
recombination analysis of the Brackett lines allows us to constrain the
electron density and emission measure during the early optically thick phase
and to estimate the mass of the ejecta to be (6.0 +/- 1.5) x 10^(-4) Msun,
assuming a filling factor of unity, from later observations.
