  The activity of the Sun alternates between a solar minimum and a solar
maximum, the former corresponding to a period of "quieter" status of the
heliosphere. During solar minimum, it is in principle more straightforward to
follow eruptive events and solar wind structures from their birth at the Sun
throughout their interplanetary journey. In this paper, we report analysis of
the origin, evolution, and heliospheric impact of a series of solar transient
events that took place during the second half of August 2018, i.e. in the midst
of the late declining phase of Solar Cycle 24. In particular, we focus on two
successive coronal mass ejections (CMEs) and a following high-speed stream
(HSS) on their way towards Earth and Mars. We find that the first CME impacted
both planets, whilst the second caused a strong magnetic storm at Earth and
went on to miss Mars, which nevertheless experienced space weather effects from
the stream interacting region (SIR) preceding the HSS. Analysis of
remote-sensing and in-situ data supported by heliospheric modelling suggests
that CME--HSS interaction resulted in the second CME rotating and deflecting in
interplanetary space, highlighting that accurately reproducing the ambient
solar wind is crucial even during "simpler" solar minimum periods. Lastly, we
discuss the upstream solar wind conditions and transient structures responsible
for driving space weather effects at Earth and Mars.
