  We present a multi-wavelength study of the IR bubble G24.136+00.436. The
J=1-0 observations of $^{12}$CO, $^{13}$CO and C$^{18}$O were carried out with
the Purple Mountain Observatory 13.7 m telescope. Molecular gas with a velocity
of 94.8 km s$^{-1}$ is found prominently in the southeast of the bubble,
shaping as a shell with a total mass of $\sim2\times10^{4}$ $M_{\odot}$. It is
likely assembled during the expansion of the bubble. The expanding shell
consists of six dense cores. Their dense (a few of $10^{3}$ cm$^{-3}$) and
massive (a few of $10^{3}$ $M_{\odot}$) characteristics coupled with the broad
linewidths ($>$ 2.5 km s$^{-1}$) suggest they are promising sites of forming
high-mass stars or clusters. This could be further consolidated by the
detection of compact HII regions in Cores A and E. We tentatively identified
and classified 63 candidate YSOs based on the \emph{Spitzer} and UKIDSS data.
They are found to be dominantly distributed in regions with strong emission of
molecular gas, indicative of active star formation especially in the shell. The
HII region inside the bubble is mainly ionized by a $\sim$O8V star(s), of the
dynamical age $\sim$1.6 Myr. The enhanced number of candidate YSOs and
secondary star formation in the shell as well as time scales involved, indicate
a possible scenario of triggering star formation, signified by the "collect and
collapse" process.
